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• Malware - Technical anlaysis

  - by nullptr

  Note: Please do not mod down or close. Im not a stupid PC user asking to fix my pc problem. I am intrigued and am having a deep technical look at whats going on. I have come across a Windows XP machine that is sending unwanted p2p traffic. I have done a 'netstat -b' command and explorer.exe is sending out the traffic. When I kill this process the traffic stops and obviously Windows Explorer dies. Here is the header of the stream from the Wireshark dump (x.x.x.x) is the machines IP. GNUTELLA CONNECT/0.6 Listen-IP: x.x.x.x:8059 Remote-IP: 76.164.224.103 User-Agent: LimeWire/5.3.6 X-Requeries: false X-Ultrapeer: True X-Degree: 32 X-Query-Routing: 0.1 X-Ultrapeer-Query-Routing: 0.1 X-Max-TTL: 3 X-Dynamic-Querying: 0.1 X-Locale-Pref: en GGEP: 0.5 Bye-Packet: 0.1 GNUTELLA/0.6 200 OK Pong-Caching: 0.1 X-Ultrapeer-Needed: false Accept-Encoding: deflate X-Requeries: false X-Locale-Pref: en X-Guess: 0.1 X-Max-TTL: 3 Vendor-Message: 0.2 X-Ultrapeer-Query-Routing: 0.1 X-Query-Routing: 0.1 Listen-IP: 76.164.224.103:15649 X-Ext-Probes: 0.1 Remote-IP: x.x.x.x GGEP: 0.5 X-Dynamic-Querying: 0.1 X-Degree: 32 User-Agent: LimeWire/4.18.7 X-Ultrapeer: True X-Try-Ultrapeers: 121.54.32.36:3279,173.19.233.80:3714,65.182.97.15:5807,115.147.231.81:9751,72.134.30.181:15810,71.59.97.180:24295,74.76.84.250:25497,96.234.62.221:32344,69.44.246.38:42254,98.199.75.23:51230 GNUTELLA/0.6 200 OK So it seems that the malware has hooked into explorer.exe and hidden its self quite well as a Norton Scan doesn't pick anything up. I have looked in Windows firewall and it shouldn't be letting this traffic through. I have had a look into the messages explorer.exe is sending in Spy++ and the only related ones I can see are socket connections etc... My question is what can I do to look into this deeper? What does malware achieve by sending p2p traffic? I know to fix the problem the easiest way is to reinstall Windows but I want to get to the bottom of it first, just out of interest. Edit: Had a look at Deoendency Walker and Process Explorer. Both great tools. Here is a image of the TCP connections for explorer.exe in Process Explorer http://img210.imageshack.us/img210/3563/61930284.gif

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• FTP could not connect after applying local DNS(private DNS)

  - by Rahul

  I made a software router in CentOS linux and in that made a DNS server. I am using centOS 6..4 for making DNS i applied following steps: changed the host name = abc.zoom.com and domain name = zoom.com. then did changes in the named.rfc.1912 file as per rename named.localhost = forward and named.loopback = reverse in forward lookups i changed zone "zoom.com" IN { type master; file "forward"; allow-update { none; }; and in reverse lookups i changed zone "x.168.192.in-addr.arpa" IN { type master; file "reverse"; allow-update { none; }; and then did changes in the named.conf file options { listen-on port 53 {192.168.x.x;}; listen-on-v6 port 53 { ::1; }; directory "/var/named"; dump-file "/var/named/data/cache_dump.db"; statistics-file "/var/named/data/named_stats.txt"; memstatistics-file "/var/named/data/named_mem_stats.txt"; allow-query {any;}; recursion yes; 192.168.x.x is my local DNS address. then i copied lookups file in /var/named and edited the file "forward" $TTL 1D @ IN SOA abc.zoom.com. rahul.abc.zoom.com. ( 0 ; serial 1D ; refresh 1H ; retry 1W ; expire 3H ) ; minimum NS abc.zoom.com. abc A 192.168.x.x and for " reverse" $TTL 1D @ IN SOA abc.zoom.com. rahul.abc.zoom.com.( 0 ; serial 1D ; refresh 1H ; retry 1W ; expire 3H ) ; minimum NS abc.zoom.com. x PTR abc.zoom.com. when i put the public ip details in the Eth0 it was automatically redirect in to the resolve.conf when i checked through dig command the answer, query all were 1. my system is itself a Software router.In gateway of my all local machine i give my system ip address. however my DNS and Gateway IP is same. Now the problem is that. i gave the static ips to all my local machines when i give the DNS which i made i.e 192.168.x.x that time my ftp is not connect in filezilla software E.g: host : pqr.zoom.com ("zoom.com" is my local domain name) username : pqr password : pqr gives an error: Error: Connection timed out Error: Could not connect to server but if i give the public DNS address it get connected. i want to solve this problem please give solution on this.

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• Seg Fault when using std::string on an embedded Linux platform

  - by Brad

  Hi, I have been working for a couple of days on a problem with my application running on an embedded Arm Linux platform. Unfortunately the platform precludes me from using any of the usual useful tools for finding the exact issue. When the same code is run on the PC running Linux, I get no such error. In the sample below, I can reliably reproduce the problem by uncommenting the string, list or vector lines. Leaving them commented results in the application running to completion. I expect that something is corrupting the heap, but I cannot see what? The program will run for a few seconds before giving a segmentation fault. The code is compiled using a arm-linux cross compiler: arm-linux-g++ -Wall -otest fault.cpp -ldl -lpthread arm-linux-strip test Any ideas greatly appreciated. #include <stdio.h> #include <vector> #include <list> #include <string> using namespace std; ///////////////////////////////////////////////////////////////////////////// class TestSeg { static pthread_mutex_t _logLock; public: TestSeg() { } ~TestSeg() { } static void* TestThread( void *arg ) { int i = 0; while ( i++ < 10000 ) { printf( "%d\n", i ); WriteBad( "Function" ); } pthread_exit( NULL ); } static void WriteBad( const char* sFunction ) { pthread_mutex_lock( &_logLock ); printf( "%s\n", sFunction ); //string sKiller; // <----------------------------------Bad //list<char> killer; // <----------------------------------Bad //vector<char> killer; // <----------------------------------Bad pthread_mutex_unlock( &_logLock ); return; } void RunTest() { int threads = 100; pthread_t _rx_thread[threads]; for ( int i = 0 ; i < threads ; i++ ) { pthread_create( &_rx_thread[i], NULL, TestThread, NULL ); } for ( int i = 0 ; i < threads ; i++ ) { pthread_join( _rx_thread[i], NULL ); } } }; pthread_mutex_t TestSeg::_logLock = PTHREAD_MUTEX_INITIALIZER; int main( int argc, char *argv[] ) { TestSeg seg; seg.RunTest(); pthread_exit( NULL ); }

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• JVM throws OutOfMemory during gc though there are plenty memory left...

  - by Shu L.

  I have my java application configured to use 5G memory. I got an OutOfMemory out of blue. I inspected the gc log and found plenty of memory left: young generation occupies 4% allocated space, tenure generation occupancy is 5% and perm generation is 43%. I am puzzled why JVM throws an OutOfMemory at the gc time. Does anyone know why this is happening? Your help is greatly appreciated. JVM memory and gc settings: -server -Xms5g -Xmx5g -Xss256k -XX:NewSize=2g -XX:MaxNewSize=2g -XX:+UseParallelOldGC -XX:+UseTLAB -XX:SurvivorRatio=8 -XX:TargetSurvivorRatio=90 -XX:+DisableExplicitGC gc.log 2009-09-19T03:34:59.741+0000: 92836.778: [GC Desired survivor size 152567808 bytes, new threshold 1 (max 15) [PSYoungGen: 1941492K-144057K(1947072K)] 3138022K-1340830K(5092800K), 0.1947640 secs] [Times: user=0.61 sys=0.01, real=0.19 secs] 2009-09-19T03:35:29.918+0000: 92866.954: [GC Desired survivor size 152109056 bytes, new threshold 1 (max 15) [PSYoungGen: 1941625K-144049K(1948608K)] 3138398K-1341080K(5094336K), 0.1942000 secs] [Times: user=0.61 sys=0.01, real=0.20 secs] 2009-09-19T03:35:56.883+0000: 92893.920: [GC Desired survivor size 156565504 bytes, new threshold 1 (max 15) [PSYoungGen: 1567994K-115427K(1915072K)] 2765026K-1312820K(5060800K), 0.1586320 secs] [Times: user=0.50 sys=0.01, real=0.16 secs] 2009-09-19T03:35:57.042+0000: 92894.079: [GC Desired survivor size 179961856 bytes, new threshold 1 (max 15) [PSYoungGen: 115427K-0K(1898560K)] 1312820K-1313987K(5044288K), 0.0775650 secs] [Times: user=0.42 sys=0.19, real=0.08 secs] 2009-09-19T03:35:57.120+0000: 92894.157: [Full GC [PSYoungGen: 0K-0K(1898560K)] [ParOldGen: 1313987K-159522K(3145728K)] 1313987K-159522K(5044288K) [PSPermGen: 20025K-19942K(40256K)], 0.56923 00 secs] [Times: user=2.18 sys=0.05, real=0.57 secs] 2009-09-19T03:35:57.690+0000: 92894.726: [GC Desired survivor size 197066752 bytes, new threshold 1 (max 15) [PSYoungGen: 0K-0K(1745728K)] 159522K-159522K(4891456K), 0.0072590 secs] [Times: user=0.01 sys=0.00, real=0.00 secs] 2009-09-19T03:35:57.698+0000: 92894.734: [Full GC [PSYoungGen: 0K-0K(1745728K)] [ParOldGen: 159522K-158627K(3145728K)] 159522K-158627K(4891456K) [PSPermGen: 19942K-19934K(45504K)], 0.3280480 secs] [Times: user=1.46 sys=0.00, real=0.33 secs] Heap PSYoungGen total 1745728K, used 87233K [0x00002aab73650000, 0x00002aabf3650000, 0x00002aabf3650000) eden space 1745664K, 4% used [0x00002aab73650000,0x00002aab78b80778,0x00002aabddf10000) from space 64K, 0% used [0x00002aabddf10000,0x00002aabddf10000,0x00002aabddf20000) to space 192448K, 0% used [0x00002aabe7a60000,0x00002aabe7a60000,0x00002aabf3650000) ParOldGen total 3145728K, used 158627K [0x00002aaab3650000, 0x00002aab73650000, 0x00002aab73650000) object space 3145728K, 5% used [0x00002aaab3650000,0x00002aaabd138d28,0x00002aab73650000) PSPermGen total 45504K, used 19965K [0x00002aaaae250000, 0x00002aaab0ec0000, 0x00002aaab3650000) object space 45504K, 43% used [0x00002aaaae250000,0x00002aaaaf5cf668,0x00002aaab0ec0000) I am on 64-bit Linux and JRE 1.6.0_10: $uname -a Linux x 2.6.24-etchnhalf.1-amd64 #1 SMP Tue Oct 14 03:11:45 UTC 2008 x86_64 GNU/Linux $java -version java version "1.6.0_10" Java(TM) SE Runtime Environment (build 1.6.0_10-b33) Java HotSpot(TM) 64-Bit Server VM (build 11.0-b15, mixed mode)

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• Windows 7 file-based backup service

  - by Ben Voigt

  I'm looking for a good replacement for Lazy Mirror, since it doesn't support Windows 7 well. Pros: One of the things I really loved about Lazy Mirror is that it always maintains a "full" backup, but does so by only copying modified files. As each file was copied, the old version got archived (moved to an out-of-the-way location). So after mirroring ran, there'd be a complete copy of the file system, which could even be booted if necessary. At the same time, extra space on the backup media was used to store as many older versions of files as possible, without wasting space storing multiple copies of the same version. It seems that with Windows 7 backup, there'd be wasted space storing the same data in both the system image and file backup. It was completely file-based, but also aware of the registry (it had a feature to dump the live registry to hive files in the correct format). The backups were normal NTFS filesystems, no special tool was needed to read them. It automatically cleaned out the oldest previous versions when space ran out (unlike Windows 7 backup which apparently simply starts failing the the backup media fills.) It copied all file attributes including security. Cons: It doesn't deal well with junction points, symbolic links, and hard links. It didn't run as a service without lots of help from firesrv or srvany, and then you couldn't interact with the GUI. Running as a service was necessary to be able to mirror protected OS files. It didn't have open file handling, except for registry hives. I guess that the file-by-file archive and replacement could leave mismatched sets of files, if the mirror was interrupted. This would be the advantage of incremental backup techniques that require old full backup + all intermediate incremental backups to restore. But I don't see this as presenting much of a problem, you'd really only have a boot failure if you had a mixture of pre- and post-service pack files, and I can run a full image backup using another tool before applying a service pack. Does anyone know of a tool that does both full-system backup and storage of old versions of files like Lazy Mirror did (without storing the same data multiple times), and also can run as a service in Windows 7? Free is best of course, but a reasonably priced paid program (e.g. It would be absolutely awesome if it also triggered a backup/mirror pass when a particular external drive was plugged in and generated popup warnings if backups hadn't been run recently)

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• Freetype2 failing under WoW64

  - by Necrolis

  I built a tff to D3D texture function using freetype2(2.3.9) to generate grayscale maps from the fonts. it works great under native win32, however, on WoW64 it just explodes (well, FT_Done and FT_Load_Glyph do). from some debugging, it seems to be a problem with HeapFree as called by free from FT_Free. I know it should work, as games like WCIII, which to the best of my knowledge use freetype2, run fine, this is my code, stripped of the D3D code(which causes no problems on its own): FT_Face pFace = NULL; FT_Error nError = 0; FT_Byte* pFont = static_cast<FT_Byte*>(ARCHIVE_LoadFile(pBuffer,&nSize)); if((nError = FT_New_Memory_Face(pLibrary,pFont,nSize,0,&pFace)) == 0) { FT_Set_Char_Size(pFace,nSize << 6,nSize << 6,96,96); for(unsigned char c = 0; c < 95; c++) { if(!FT_Load_Glyph(pFace,FT_Get_Char_Index(pFace,c + 32),FT_LOAD_RENDER)) { FT_Glyph pGlyph; if(!FT_Get_Glyph(pFace->glyph,&pGlyph)) { LOG("GET: %c",c + 32); FT_Glyph_To_Bitmap(&pGlyph,FT_RENDER_MODE_NORMAL,0,1); FT_BitmapGlyph pGlyphMap = reinterpret_cast<FT_BitmapGlyph>(pGlyph); FT_Bitmap* pBitmap = &pGlyphMap->bitmap; const size_t nWidth = pBitmap->width; const size_t nHeight = pBitmap->rows; //add to texture atlas } } } } else { FT_Done_Face(pFace); delete pFont; return FALSE; } FT_Done_Face(pFace); delete pFont; return TRUE; } ARCHIVE_LoadFile returns blocks allocated with new. As a secondary question, I would like to render a font using pixel sizes, I came across FT_Set_Pixel_Sizes, but I'm unsure as to whether this stretches the font to fit the size, or bounds it to a size. what I would like to do is render all the glyphs at say 24px (MS Word size here), then turn it into a signed distance field in a 32px area. Update After much fiddling, I got a test app to work, which leads me to think the problems are arising from threading, as my code is running in a secondary thread. I have compiled freetype into a static lib using the multithread DLL, my app uses the multithreaded libs. gonna see if i can set up a multithreaded test. Also updated to 2.4.4, to see if the problem was a known but fixed bug, didn't help however. Update 2 After some more fiddling, it turns out I wasn't using the correct lib for 2.4.4 -.- after fixing that, the test app works 100%, but the main app still crashes when FT_Done_Face is called, still seems to be a crash in the memory heap management of windows. is it possible that there is a bug in freetype2 that makes it blow up under user threads?

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• RHEL 6.x on Rackspace Cloud and Dedicated hardware experiencing Redis Timeouts

  - by zhallett

  I just recently set up a mixture of RHEL 6.1 Rackspace cloud hosts and RHEL 6.2 dedicated hosts using Rackconnect. I am experiencing intermittent Redis timeouts from within our Rails 3.2.8 app with Redis 2.4.16 running on the RHEL 6.2 dedicated hosts. There is no network latency or packet loss. Also there are no errors on any interfaces on our cloud or dedicated servers or on the managed firewall from Rackspace. When Redis timesout, there is nothing logged within redis even though it is set up to do debug logging. The only error we receive is from Airbrake saying there was a Redis timeout. Network topology: RHEL 6.1 cloud hosts <--> Alert logic IDS <--> Cisco ASA 5510 <--> RHEL 6.2 dedicated hosts (web nodes) (two way NAT) (db hosts running redis) Ping from db host to web host: 64 bytes from 10.181.230.180: icmp_seq=998 ttl=64 time=0.520 ms 64 bytes from 10.181.230.180: icmp_seq=999 ttl=64 time=0.579 ms 64 bytes from 10.181.230.180: icmp_seq=1000 ttl=64 time=0.482 ms --- web1.xxxxxx.com ping statistics --- 1000 packets transmitted, 1000 received, 0% packet loss, time 999007ms rtt min/avg/max/mdev = 0.359/0.535/5.684/0.200 ms Ping from web host to db host: 64 bytes from 192.168.100.26: icmp_seq=998 ttl=64 time=0.544 ms 64 bytes from 192.168.100.26: icmp_seq=999 ttl=64 time=0.452 ms 64 bytes from 192.168.100.26: icmp_seq=1000 ttl=64 time=0.529 ms --- data1.xxxxxx.com ping statistics --- 1000 packets transmitted, 1000 received, 0% packet loss, time 999017ms rtt min/avg/max/mdev = 0.358/0.499/6.120/0.201 ms Redis config: daemonize yes pidfile /var/run/redis/6379/redis_6379.pid port 6379 timeout 0 loglevel debug logfile /var/lib/redis/log syslog-enabled yes syslog-ident redis-6379 syslog-facility local0 databases 16 save 900 1 save 300 10 save 60 10000 rdbcompression yes dbfilename dump-6379.rdb dir /var/lib/redis maxclients 10000 maxmemory-policy volatile-lru maxmemory-samples 3 appendfilename appendonly-6379.aof appendfsync everysec no-appendfsync-on-rewrite no auto-aof-rewrite-percentage 100 auto-aof-rewrite-min-size 64mb slowlog-log-slower-than 10000 slowlog-max-len 1024 vm-enabled no vm-swap-file /tmp/redis.swap vm-max-memory 0 vm-page-size 32 vm-pages 134217728 vm-max-threads 4 hash-max-zipmap-entries 512 hash-max-zipmap-value 64 list-max-ziplist-entries 512 list-max-ziplist-value 64 set-max-intset-entries 512 zset-max-ziplist-entries 128 zset-max-ziplist-value 64 activerehashing yes Redis-cli info: redis-cli info redis_version:2.4.16 redis_git_sha1:00000000 redis_git_dirty:0 arch_bits:64 multiplexing_api:epoll gcc_version:4.4.6 process_id:4174 uptime_in_seconds:79346 uptime_in_days:0 lru_clock:1064644 used_cpu_sys:13.08 used_cpu_user:19.81 used_cpu_sys_children:1.56 used_cpu_user_children:7.69 connected_clients:167 connected_slaves:0 client_longest_output_list:0 client_biggest_input_buf:0 blocked_clients:6 used_memory:15060312 used_memory_human:14.36M used_memory_rss:22061056 used_memory_peak:15265928 used_memory_peak_human:14.56M mem_fragmentation_ratio:1.46 mem_allocator:jemalloc-3.0.0 loading:0 aof_enabled:0 changes_since_last_save:166 bgsave_in_progress:0 last_save_time:1352823542 bgrewriteaof_in_progress:0 total_connections_received:286 total_commands_processed:507254 expired_keys:0 evicted_keys:0 keyspace_hits:1509 keyspace_misses:65167 pubsub_channels:0 pubsub_patterns:0 latest_fork_usec:690 vm_enabled:0 role:master db0:keys=6,expires=0 edit 1: add redis-cli info output

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• How to optimize my PostgreSQL DB for prefix search?

  - by asmaier

  I have a table called "nodes" with roughly 1.7 million rows in my PostgreSQL db =#\d nodes Table "public.nodes" Column | Type | Modifiers --------+------------------------+----------- id | integer | not null title | character varying(256) | score | double precision | Indexes: "nodes_pkey" PRIMARY KEY, btree (id) I want to use information from that table for autocompletion of a search field, showing the user a list of the ten titles having the highest score fitting to his input. So I used this query (here searching for all titles starting with "s") =# explain analyze select title,score from nodes where title ilike 's%' order by score desc; QUERY PLAN ----------------------------------------------------------------------------------------------------------------------- Sort (cost=64177.92..64581.38 rows=161385 width=25) (actual time=4930.334..5047.321 rows=161264 loops=1) Sort Key: score Sort Method: external merge Disk: 5712kB -> Seq Scan on nodes (cost=0.00..46630.50 rows=161385 width=25) (actual time=0.611..4464.413 rows=161264 loops=1) Filter: ((title)::text ~~* 's%'::text) Total runtime: 5260.791 ms (6 rows) This was much to slow for using it with autocomplete. With some information from Using PostgreSQL in Web 2.0 Applications I was able to improve that with a special index =# create index title_idx on nodes using btree(lower(title) text_pattern_ops); =# explain analyze select title,score from nodes where lower(title) like lower('s%') order by score desc limit 10; QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------ Limit (cost=18122.41..18122.43 rows=10 width=25) (actual time=1324.703..1324.708 rows=10 loops=1) -> Sort (cost=18122.41..18144.60 rows=8876 width=25) (actual time=1324.700..1324.702 rows=10 loops=1) Sort Key: score Sort Method: top-N heapsort Memory: 17kB -> Bitmap Heap Scan on nodes (cost=243.53..17930.60 rows=8876 width=25) (actual time=96.124..1227.203 rows=161264 loops=1) Filter: (lower((title)::text) ~~ 's%'::text) -> Bitmap Index Scan on title_idx (cost=0.00..241.31 rows=8876 width=0) (actual time=90.059..90.059 rows=161264 loops=1) Index Cond: ((lower((title)::text) ~>=~ 's'::text) AND (lower((title)::text) ~<~ 't'::text)) Total runtime: 1325.085 ms (9 rows) So this gave me a speedup of factor 4. But can this be further improved? What if I want to use '%s%' instead of 's%'? Do I have any chance of getting a decent performance with PostgreSQL in that case, too? Or should I better try a different solution (Lucene?, Sphinx?) for implementing my autocomplete feature?

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• Help me stabilize this jRun configuration (CF9/Win2k3/IIS6)

  - by jfrobishow

  Not sure if this would be better suited for ServerFault, but since I am not an admin but a developer I figured I would try SO. We've been struggling to keep our multi-server configuration stable for quite some time now. At the end of last month we were running under CF 7.0.2 on a two servers setup (one instance each). At that point we managed to get our uptime to around 1 week per instance before they would restart by themselves. Since the beginning of the month we upgraded to CF 9 and we're back to square one with multi-restart a day. Our current configuration is 2 Win2k3 servers, running a cluster of 4 instances, 2 instances per server. At this point we are pretty certain this is due to improper JVM settings. We've been toying with them and while some are more stable than others we never quite got it right. From the default: java.args=-server -Xmx512m -Dsun.io.useCanonCaches=false -XX:MaxPermSize=192m -XX:+UseParallelGC -Dcoldfusion.rootDir={application.home}/ To currently: java.args=-server -Xmx896m -Dsun.io.useCanonCaches=false -XX:MaxPermSize=512m -XX:SurvivorRatio=8 -XX:TargetSurvivorRatio=90 -XX:+UseParallelGC -Dcoldfusion.rootDir={application.home}/ -verbose:gc -Xloggc:c:/Jrun4/logs/gc/gcInstance1b.log We have determined that we do need more than the default 512MB simply by monitoring with FusionReactor, on average our amount of memory consumed is hovering in the mid 300MB and can go up to low 700MB under heavy load. Most of the crash will be logged in jrun4/bin/hs_err_pid*.log always an "Out of swap space" I've attached links to the hs_err and garbage collector log file from yesterday at the bottom of the post. The relevant part is (I think) this: Heap PSYoungGen total 89856K, used 19025K [0x55490000, 0x5b6f0000, 0x5b810000) eden space 79232K, 16% used [0x55490000,0x561a64c0,0x5a1f0000) from space 10624K, 52% used [0x5ac90000,0x5b20e2f8,0x5b6f0000) to space 10752K, 0% used [0x5a1f0000,0x5a1f0000,0x5ac70000) PSOldGen total 460416K, used 308422K [0x23810000, 0x3f9b0000, 0x55490000) object space 460416K, 66% used [0x23810000,0x36541bb8,0x3f9b0000) PSPermGen total 107520K, used 106079K [0x03810000, 0x0a110000, 0x23810000) object space 107520K, 98% used [0x03810000,0x09fa7e40,0x0a110000) From it, I gather that its the PSPermGen that is full (most logs will show the same before a crash), which is why we increased MaxPermSize but the total still show as 107520K!??! No one here is a jRun expert, so any help or even ideas on what to try next would be greatly appreciated!! The log files: Sorry I know sendspace isn't the friendliest of places - if you have other host suggestion for log files let me know and I'll update the post (SO doesn't like them inline, it blows up the format of the post). The hs_err log file: http://www.sendspace.com/file/fgak8l The gc log: http://www.sendspace.com/file/w0r2ct

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• How to I serialize a large graph of .NET object into a SQL Server BLOB without creating a large bu

  - by Ian Ringrose

  We have code like: ms = New IO.MemoryStream bin = New System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bin.Serialize(ms, largeGraphOfObjects) dataToSaveToDatabase = ms.ToArray() // put dataToSaveToDatabase in a Sql server BLOB But the memory steam allocates a large buffer from the large memory heap that is giving us problems. So how can we stream the data without needing enough free memory to hold the serialized objects. I am looking for a way to get a Stream from SQL server that can then be passed to bin.Serialize() so avoiding keeping all the data in my processes memory. Likewise for reading the data back... Some more background. This is part of a complex numerical processing system that processes data in near real time looking for equipment problems etc, the serialization is done to allow a restart when there is a problem with data quality from a data feed etc. (We store the data feeds and can rerun them after the operator has edited out bad values.) Therefore we serialize the object a lot more often then we de-serialize them. The objects we are serializing include very large arrays mostly of doubles as well as a lot of small “more normal” objects. We are pushing the memory limit on a 32 bit system and make the garage collector work very hard. (Effects are being made elsewhere in the system to improve this, e.g. reusing large arrays rather then create new arrays.) Often the serialization of the state is the last straw that courses an out of memory exception; our peak memory usage is while this serialization is being done. I think we get large memory pool fragmentation when we de-serialize the object, I expect there are also other problem with large memory pool fragmentation given the size of the arrays. (This has not yet been investigated, as the person that first looked at this is a numerical processing expert, not a memory management expert.) Are customers use a mix of Sql Server 2000, 2005 and 2008 and we would rather not have different code paths for each version of Sql Server if possible. We can have many active models at a time (in different process, across many machines), each model can have many saved states. Hence the saved state is stored in a database blob rather then a file. As the spread of saving the state is important, I would rather not serialize the object to a file, and then put the file in a BLOB one block at a time. Other related questions I have asked How to Stream data from/to SQL Server BLOB fields? Is there a SqlFileStream like class that works with Sql Server 2005?

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• Understanding CLR 2.0 Memory Model

  - by Eloff

  Joe Duffy, gives 6 rules that describe the CLR 2.0+ memory model (it's actual implementation, not any ECMA standard) I'm writing down my attempt at figuring this out, mostly as a way of rubber ducking, but if I make a mistake in my logic, at least someone here will be able to catch it before it causes me grief. Rule 1: Data dependence among loads and stores is never violated. Rule 2: All stores have release semantics, i.e. no load or store may move after one. Rule 3: All volatile loads are acquire, i.e. no load or store may move before one. Rule 4: No loads and stores may ever cross a full-barrier (e.g. Thread.MemoryBarrier, lock acquire, Interlocked.Exchange, Interlocked.CompareExchange, etc.). Rule 5: Loads and stores to the heap may never be introduced. Rule 6: Loads and stores may only be deleted when coalescing adjacent loads and stores from/to the same location. I'm attempting to understand these rules. x = y y = 0 // Cannot move before the previous line according to Rule 1. x = y z = 0 // equates to this sequence of loads and stores before possible re-ordering load y store x load 0 store z Looking at this, it appears that the load 0 can be moved up to before load y, but the stores may not be re-ordered at all. Therefore, if a thread sees z == 0, then it also will see x == y. If y was volatile, then load 0 could not move before load y, otherwise it may. Volatile stores don't seem to have any special properties, no stores can be re-ordered with respect to each other (which is a very strong guarantee!) Full barriers are like a line in the sand which loads and stores can not be moved over. No idea what rule 5 means. I guess rule 6 means if you do: x = y x = z Then it is possible for the CLR to delete both the load to y and the first store to x. x = y z = y // equates to this sequence of loads and stores before possible re-ordering load y store x load y store z // could be re-ordered like this load y load y store x store z // rule 6 applied means this is possible? load y store x // but don't pop y from stack (or first duplicate item on top of stack) store z What if y was volatile? I don't see anything in the rules that prohibits the above optimization from being carried out. This does not violate double-checked locking, because the lock() between the two identical conditions prevents the loads from being moved into adjacent positions, and according to rule 6, that's the only time they can be eliminated. So I think I understand all but rule 5, here. Anyone want to enlighten me (or correct me or add something to any of the above?)

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• Java map / nio / NFS issue causing a VM fault: "a fault occurred in a recent unsafe memory access op

  - by Matthew Bloch

  I have written a parser class for a particular binary format (nfdump if anyone is interested) which uses java.nio's MappedByteBuffer to read through files of a few GB each. The binary format is just a series of headers and mostly fixed-size binary records, which are fed out to the called by calling nextRecord(), which pushes on the state machine, returning null when it's done. It performs well. It works on a development machine. On my production host, it can run for a few minutes or hours, but always seems to throw "java.lang.InternalError: a fault occurred in a recent unsafe memory access operation in compiled Java code", fingering one of the Map.getInt, getShort methods, i.e. a read operation in the map. The uncontroversial (?) code that sets up the map is this: /** Set up the map from the given filename and position */ protected void open() throws IOException { // Set up buffer, is this all the flexibility we'll need? channel = new FileInputStream(file).getChannel(); MappedByteBuffer map1 = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size()); map1.load(); // we want the whole thing, plus seems to reduce frequency of crashes? map = map1; // assumes the host writing the files is little-endian (x86), ought to be configurable map.order(java.nio.ByteOrder.LITTLE_ENDIAN); map.position(position); } and then I use the various map.get* methods to read shorts, ints, longs and other sequences of bytes, before hitting the end of the file and closing the map. I've never seen the exception thrown on my development host. But the significant point of difference between my production host and development is that on the former, I am reading sequences of these files over NFS (probably 6-8TB eventually, still growing). On my dev machine, I have a smaller selection of these files locally (60GB), but when it blows up on the production host it's usually well before it gets to 60GB of data. Both machines are running java 1.6.0_20-b02, though the production host is running Debian/lenny, the dev host is Ubuntu/karmic. I'm not convinced that will make any difference. Both machines have 16GB RAM, and are running with the same java heap settings. I take the view that if there is a bug in my code, there is enough of a bug in the JVM not to throw me a proper exception! But I think it is just a particular JVM implementation bug due to interactions between NFS and mmap, possibly a recurrence of 6244515 which is officially fixed. I already tried adding in a "load" call to force the MappedByteBuffer to load its contents into RAM - this seemed to delay the error in the one test run I've done, but not prevent it. Or it could be coincidence that was the longest it had gone before crashing! If you've read this far and have done this kind of thing with java.nio before, what would your instinct be? Right now mine is to rewrite it without nio :)

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• Android problem: BufferedReader wont read whole stream into a string

  - by Levara

  Hi all! I'm making an android program that retrieves content of a webpage using HttpURLConnection. I'm new to both Java and Android. Problem is: Reader reads whole page source, but in the last while iteration it doesn't append to stringBuffer that last part. Using debbuger I have determined that, in the last loop iteration, string buff is created, but stringBuffer just doesnt append it. I need to parse retrieved content. Is there any better way to handle the content for parsing than using strings. I've read on numerous other sites that string size in Java is limited only by available heap size. Anyone know what could be the problem. Btw feel free to suggest any improvements to the code. Thanks! URL u; try { u = new URL("http://feeds.timesonline.co.uk/c/32313/f/440134/index.rss"); HttpURLConnection c = (HttpURLConnection) u.openConnection(); c.setRequestProperty("User-agent","Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; InfoPath.1; .NET CLR 2.0.50727)"); c.setRequestMethod("GET"); c.setDoOutput(true); c.setReadTimeout(3000); c.connect(); StringBuffer stringBuffer = new StringBuffer(""); InputStream in = c.getInputStream(); InputStreamReader inp = new InputStreamReader(in); BufferedReader reader = new BufferedReader(inp); char[] buffer = new char[3072]; int len1 = 0; while ( (len1 = reader.read(buffer)) != -1 ) { String buff = new String(buffer,0,len1); stringBuffer.append(buff); } String stranica = new String(stringBuffer); c.disconnect(); reader.close(); inp.close(); in.close();

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• PHP Processes reaching limit along with FastCGI timeouts

  - by Constant M

  I have a problem similar to http://stackoverflow.com/questions/1168384/how-to-troubleshoot-php-processes, but with a twist. We have a couple of managed servers that recently migrated to FastCGI. Since then we've been having problems. We have a content management system at a central place that we manage all our sites with. All the sites run on the same managed server. So basically its one PHP script that generates pages on the same server. The catch comes in where it works perfectly on some, and gives FCGI timeout errors on others. At the same time our support is saying that the PHP processes heap up to their limit and then causes Apache to stop working. I'm convinced this is a fault on their side, but would like to get my side clean too. Anyway have any suggestions where I can start looking for what's going wrong? I know it's a really broad question, but any help or pointers would be great. Thanks Just to add to that, here's a PS printout from support: happyh 13853 21556 0 01:04 ? 00:00:00 /usr/bin/php5-cgi happyh 13869 13853 0 01:04 ? 00:00:00 /usr/bin/php5-cgi mamedc 13914 21556 0 05:14 ? 00:00:00 /usr/bin/php5-cgi wealthf 13947 21556 0 01:21 ? 00:00:00 /usr/bin/php5-cgi wealthf 13961 13947 0 01:21 ? 00:00:00 /usr/bin/php5-cgi mamedc 14032 13914 0 05:14 ? 00:00:00 /usr/bin/php5-cgi lookgrt 14157 21556 0 04:47 ? 00:00:00 /usr/bin/php5-cgi lookgrt 14178 14157 0 04:47 ? 00:00:00 /usr/bin/php5-cgi wolfie 14262 21556 0 01:08 ? 00:00:00 /usr/bin/php5-cgi wolfie 14276 14262 0 01:08 ? 00:00:00 /usr/bin/php5-cgi yaukrl 14352 21556 0 01:21 ? 00:00:00 /usr/bin/php5-cgi yaukrl 14361 14352 0 01:21 ? 00:00:00 /usr/bin/php5-cgi itpays2 14538 21556 0 01:33 ? 00:00:00 /usr/bin/php5-cgi itpays2 14547 14538 0 01:33 ? 00:00:00 /usr/bin/php5-cgi brichmbx 14732 21556 0 04:47 ? 00:00:00 /usr/bin/php5-cgi brichmbx 14803 14732 0 04:47 ? 00:00:00 /usr/bin/php5-cgi greatl 14969 21556 0 01:00 ? 00:00:00 /usr/bin/php5-cgi

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• C++ Program Always Crashes While doing a std::string assign

  - by bbazso

  I have been trying to debug a crash in my application that crashes (i.e. asserts a * glibc detected free(): invalid pointer: 0x000000000070f0c0 **) while I'm trying to do a simple assign to a string. Note that I'm compiling on a linux system with gcc 4.2.4 with an optimization level set to -O2. With -O0 the application no longer crashes. E.g. std::string abc; abc = "testString"; but if I changed the code as follows it no longer crashes std::string abc("testString"); So again I scratched my head! But the interesting pattern was that the crash moved later on in the application, AGAIN at another string. I found it weird that the application was continuously crashing on a string assign. A typical crash backtrace would look as follows: #0 0x00007f2c2663bfb5 in raise () from /lib64/libc.so.6 (gdb) bt #0 0x00007f2c2663bfb5 in raise () from /lib64/libc.so.6 #1 0x00007f2c2663dbc3 in abort () from /lib64/libc.so.6 #2 0x00000000004d8cb7 in people_streamingserver_sighandler (signum=6) at src/peoplestreamingserver.cpp:487 #3 <signal handler called> #4 0x00007f2c2663bfb5 in raise () from /lib64/libc.so.6 #5 0x00007f2c2663dbc3 in abort () from /lib64/libc.so.6 #6 0x00007f2c26680ce0 in ?? () from /lib64/libc.so.6 #7 0x00007f2c270ca7a0 in std::string::assign (this=0x7f2c21bc8d20, __str=<value optimized out>) at /home/bbazso/ThirdParty/sources/gcc-4.2.4/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:238 #8 0x00007f2c21bd874a in PEOPLESProtocol::GetStreamName (this=<value optimized out>, pRawPath=0x2342fd8 "rtmp://127.0.0.1/mp4:pop.mp4", lStreamName=@0x7f2c21bc8d20) at /opt/trx-HEAD/gcc/4.2.4/lib/gcc/x86_64-pc-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/basic_string.h:491 #9 0x00007f2c21bd9daa in PEOPLESProtocol::SignalProtocolCreated (pProtocol=0x233a4e0, customParameters=@0x7f2c21bc8de0) at peoplestreamer/src/peoplesprotocol.cpp:240 This was really weird behavior and so I started to poke around further in my application to see if there was some sort of memory corruption (either heap or stack) error that could be occurring that could be causing this weird behavior. I even checked for ptr corruptions and came up empty handed. In addition to visual inspection of the code I also tried the following tools: Valgrind using both memcheck and exp-ptrcheck electric fence libsafe I compiled with -fstack-protector-all in gcc I tried MALLOC_CHECK_ set to 2 I ran my code through lint checks as well as cppcheck (to check for mistakes) And I stepped through the code using gdb So I tried a lot of stuff and still came up empty handed. So I was wondering if it could be something like a linker issue or a library issue of some sort that could be causing this problem. Are there any know issues with the std::string that make is susceptible to crashing in -O2 or maybe it has nothing to do with the optimization level? But the only pattern that I can see thus far in my problem is that it always seems to crash on a string and so I was wondering if anyone knew of any issues that my be causing this type of behavior. Thanks a lot!

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• I am unable to connect to my netbook from any machine on my network until the netbook has pinged it

  - by Samuel Husky

  I have a rather strange issue with my netbook on my local network. When trying to connect to it in any way from a remote system it does not appear to find it. However if I get the netbook to ping the machine trying to connect it mystically appears to work. Below is the ping test from my main PC to the netbook. C:\Users\Sam>ping 192.168.8.102 Pinging 192.168.8.102 with 32 bytes of data: Reply from 192.168.8.100: Destination host unreachable. Reply from 192.168.8.100: Destination host unreachable. Reply from 192.168.8.100: Destination host unreachable. Reply from 192.168.8.100: Destination host unreachable. Ping statistics for 192.168.8.102: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Now a ping from the netbook to my main PC sam@malamute ~ $ ping 192.168.8.100 PING 192.168.8.100 (192.168.8.100) 56(84) bytes of data. 64 bytes from 192.168.8.100: icmp_req=1 ttl=128 time=2.46 ms 64 bytes from 192.168.8.100: icmp_req=2 ttl=128 time=0.835 ms 64 bytes from 192.168.8.100: icmp_req=3 ttl=128 time=1.60 ms 64 bytes from 192.168.8.100: icmp_req=4 ttl=128 time=1.32 ms 64 bytes from 192.168.8.100: icmp_req=5 ttl=128 time=1.34 ms ^C --- 192.168.8.100 ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 4004ms rtt min/avg/max/mdev = 0.835/1.514/2.460/0.536 ms And the same ping again from the main PC after the netbook has made a connection to it C:\Users\Sam>ping 192.168.8.102 Pinging 192.168.8.102 with 32 bytes of data: Reply from 192.168.8.102: bytes=32 time=1ms TTL=64 Reply from 192.168.8.102: bytes=32 time=1ms TTL=64 Reply from 192.168.8.102: bytes=32 time=1ms TTL=64 Reply from 192.168.8.102: bytes=32 time=1ms TTL=64 Ping statistics for 192.168.8.102: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 1ms, Maximum = 1ms, Average = 1ms The netbook is running Gentoo and is currently connected via wireless. My main PC is running Windows 7 however I get the same result no matter what PC I use on this network. Please see this example from a CentOS machine on the same network [root@tiger ~]# ping 192.168.8.102 PING 192.168.8.102 (192.168.8.102) 56(84) bytes of data. From 192.168.8.200 icmp_seq=2 Destination Host Unreachable From 192.168.8.200 icmp_seq=3 Destination Host Unreachable From 192.168.8.200 icmp_seq=4 Destination Host Unreachable --- 192.168.8.102 ping statistics --- 6 packets transmitted, 0 received, +3 errors, 100% packet loss, time 5000ms , pipe 3 If you need any more information or require logs or config files please let me know and any assistance is greatly appreciated. Additional info: No responses on TCP dump from the netbook. Same result when booting into Ubuntu from a USB key. No issue when using a wired Ethernet connection.

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• Recover harddrive data

  - by gameshints

  I have a dell laptop that recently "died" (It would get the blue screen of death upon starting) and the hard drive would make a weird cyclic clicking noises. I wanted to see if I could use some tools on my linux machine to recover the data, so I plugged it into there. If I run "fdisk" I get: Disk /dev/sdb: 20.0 GB, 20003880960 bytes 64 heads, 32 sectors/track, 19077 cylinders Units = cylinders of 2048 * 512 = 1048576 bytes Disk identifier: 0x64651a0a Disk /dev/sdb doesn't contain a valid partition table Fine, the partition table is messed up. However if I run "testdisk" in attempt to fix the table, it freezes at this point, making the same cyclical clicking noises: Disk /dev/sdb - 20 GB / 18 GiB - CHS 19078 64 32 Analyse cylinder 158/19077: 00% I don't really care about the hard drive working again, and just the data, so I ran "gpart" to figure out where the partitions used to be. I got this: dev(/dev/sdb) mss(512) chs(19077/64/32)(LBA) #s(39069696) size(19077mb) * Warning: strange partition table magic 0x2A55. Primary partition(1) type: 222(0xDE)(UNKNOWN) size: 15mb #s(31429) s(63-31491) chs: (0/1/1)-(3/126/63)d (0/1/32)-(15/24/4)r hex: 00 01 01 00 DE 7E 3F 03 3F 00 00 00 C5 7A 00 00 Primary partition(2) type: 007(0x07)(OS/2 HPFS, NTFS, QNX or Advanced UNIX) (BOOT) size: 19021mb #s(38956987) s(31492-38988478) chs: (4/0/1)-(895/126/63)d (15/24/5)-(19037/21/31)r hex: 80 00 01 04 07 7E FF 7F 04 7B 00 00 BB 6F 52 02 So I tried to mount just to the old NTFS partition, but got an error: sudo mount -o loop,ro,offset=16123904 -t ntfs /dev/sdb /mnt/usb NTFS signature is missing. Ugh. Okay. But then I tried to get a raw data dump by running dd if=/dev/sdb of=/home/erik/brokenhd skip=31492 count=38956987 But the file got up to 59885568 bytes, and made the same cyclical clicking noises. Obviously there is a bad sector, but I don't know what to do about it! The data is still there... if I view that 57MB file in textpad... I can see raw data from files. How can I get my data back? Thanks for any suggestions, Solution: I was able to recover about 90% of my data: Froze harddrive in freezer Used Ddrescue to make a copy of the drive Since Ddrescue wasn't able to get enough of my drive to use testdisk to recover my partitions/file system, I ended up using photorec to recover most of my files

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• Why is mount -a not mounting fuse drive properly when executed remotely (via Fabric)?

  - by Jim D

  This is a weird bug and I'm not sure where it's coming from. Here's a quick run down of what I'm doing. I'm trying to mount a FUSE drive to an Amazon EC2 instance running Ubuntu 10.10 using s3fs (FUSE over Amazon). s3fs is compiled from source according to the instructions etc. I've also added an entry to /etc/fstab so that the drive mounts on boot. Here's what /etc/fstab looks like: # /etc/fstab: static file system information. # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 LABEL=uec-rootfs / ext4 defaults 0 0 /dev/sda2 /mnt auto defaults,nobootwait,comment=cloudconfig 0 2 /dev/sda3 none swap sw,comment=cloudconfig 0 0 s3fs#mybucket /mnt/s3/mybucket fuse default_acl=public-read,use_cache=/tmp,allow_other 0 0 So the good news is that this works fine. On reboot the connection mounts correctly. I can also do: $ sudo umount /mnt/s3/mybucket $ sudo mount -a $ mountpoint /mnt/s3/mybucket /mnt/s3/mybucket is a mountpoint Great, right? Well here's the problem. I'm using Fabric to automate the process of building and managing this instance. I noticed I was getting this error message when using Fabric to build s3fs and set up the mount process: mountpoint: /mnt/s3/mybucket: Transport endpoint is not connected I isolated it down the the problem and built a fabric task that reproduces the problem: def remount_s3fs(): sudo("mount -a") Which does: [ec2-xx-xx-xx-xx.compute-1.amazonaws.com] Executing task 'remount_s3fs' [ec2-xx-xx-xx-xx.compute-1.amazonaws.com] sudo: mount -a [And yes, I was sure to unmount it before running this task.] When I check the mount using mountpoint I get: $ mountpoint /mnt/s3/mybucket mountpoint: /mnt/s3/mybucket: Transport endpoint is not connected Done. But if I run sudo mount -a at the command line, it works. Hrm. Here is that fab task output again, this time in full debug mode: [ec2-xx-xx-xx-xx.compute-1.amazonaws.com] Executing task 'remount_s3fs' [ec2-xx-xx-xx-xx.compute-1.amazonaws.com] sudo: sudo -S -p 'sudo password:' /bin/bash -l -c "mount -a" Again, I get that transport endpoint not connected error. I've also tried copying and pasting the exact command run into my ssh session (i.e. sudo -S -p 'sudo password:' /bin/bash -l -c "mount -a") and it works fine. So...that's my problem. Any ideas?

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• Anyone else experiencing high rates of Linux server crashes during a leap second day?

  - by Bron Gondwana

  POSTMORTEM Anticlimax: only thing that died was my VPN (openvpn) link to the cluster, so there was an exciting few seconds while it re-established. Everything else was fine. Starting back ntp everywhere. If you look at Marco's blog at http://my.opera.com/marcomarongiu/blog/2012/06/01/an-humble-attempt-to-work-around-the-leap-second - he has a solution for phasing the time change over 24 hours using ntpd -x to avoid the 1 second skip. Give that a go if it matters to you. For the systems I run, the jump isn't a problem. Just today, Sat June 30th - starting soon after the start of the day GMT. We've had a handful of blades in different datacentres as managed by different teams all go dark - not responding to pings, screen blank. They're all running Debian Squeeze - with everything from stock kernel to custom 3.2.21 builds. Most are Dell M610 blades, but I've also just lost a Dell R510 and other departments have lost machines from other vendors too. There was also an older IBM x3550 which crashed and which I thought might be unrelated, but now I'm wondering. The one crash which I did get a screen dump from said: [3161000.864001] BUG: spinlock lockup on CPU#1, ntpd/3358 [3161000.864001] lock: ffff88083fc0d740, .magic: dead4ead, .owner: imapd/24737, .owner_cpu: 0 Unfortunately the blades all supposedly had kdump configured, but they died so hard that kdump didn't trigger - and they had console blanking turned on. I've disabled console blanking now, so fingers crossed I'll have more information after the next crash. Just want to know if it's a common thread or "just us". It's really odd that they're different units in different datacentres bought at different times and run by different admins (I run the FastMail.FM ones)... and now even different vendor hardware. Most of the machines which crashed had been up for weeks/months and were running 3.1 or 3.2 series kernels. The most recent crash was a machine which had only been up about 6 hours running 3.2.21. THE WORKAROUND Ok people, here's how I worked around it. disabled ntp: /etc/init.d/ntp stop created http://linux.brong.fastmail.fm/2012-06-30/fixtime.pl (code stolen from Marco, see blog posts in comments) ran fixtime.pl without an argument to see that there was a leap second set ran fixtime.pl with an argument to remove the leap second NOTE: depends on adjtimex. I've put a copy of the squeeze adjtimex binary at http://linux.brong.fastmail.fm/2012-06-30/adjtimex - it will run without dependencies on a squeeze 64 bit system. If you put it in the same directory as fixtime.pl, it will be used if the system one isn't present. Obviously if you don't have squeeze 64 bit... find your own. I'm going to start ntp again tomorrow. As an anonymous user suggested - an alternative to running adjtimex is to just set the time yourself, which will presumably also clear the leapsecond counter.

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• Autocomplete server-side implementation

  - by toluju

  What is a fast and efficient way to implement the server-side component for an autocomplete feature in an html input box? I am writing a service to autocomplete user queries in our web interface's main search box, and the completions are displayed in an ajax-powered dropdown. The data we are running queries against is simply a large table of concepts our system knows about, which matches roughly with the set of wikipedia page titles. For this service obviously speed is of utmost importance, as responsiveness of the web page is important to the user experience. The current implementation simply loads all concepts into memory in a sorted set, and performs a simple log(n) lookup on a user keystroke. The tailset is then used to provide additional matches beyond the closest match. The problem with this solution is that it does not scale. It currently is running up against the VM heap space limit (I've set -Xmx2g, which is about the most we can push on our 32 bit machines), and this prevents us from expanding our concept table or adding more functionality. Switching to 64-bit VMs on machines with more memory isn't an immediate option. I've been hesitant to start working on a disk-based solution as I am concerned that disk seek time will kill performance. Are there possible solutions that will let me scale better, either entirely in memory or with some fast disk-backed implementations? Edits: @Gandalf: For our use case it is important the the autocompletion is comprehensive and isn't just extra help for the user. As for what we are completing, it is a list of concept-type pairs. For example, possible entries are [("Microsoft", "Software Company"), ("Jeff Atwood", "Programmer"), ("StackOverflow.com", "Website")]. We are using Lucene for the full search once a user selects an item from the autocomplete list, but I am not yet sure Lucene would work well for the autocomplete itself. @Glen: No databases are being used here. When I'm talking about a table I just mean the structured representation of my data. @Jason Day: My original implementation to this problem was to use a Trie, but the memory bloat with that was actually worse than the sorted set due to needing a large number of object references. I'll read on the ternary search trees to see if it could be of use.

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• How to optimize this SQL query for a rectangular region?

  - by Andrew B.

  I'm trying to optimize the following query, but it's not clear to me what index or indexes would be best. I'm storing tiles in a two-dimensional plane and querying for rectangular regions of that plane. The table has, for the purposes of this question, the following columns: id: a primary key integer world_id: an integer foreign key which acts as a namespace for a subset of tiles tileY: the Y-coordinate integer tileX: the X-coordinate integer value: the contents of this tile, a varchar if it matters. I have the following indexes: "ywot_tile_pkey" PRIMARY KEY, btree (id) "ywot_tile_world_id_key" UNIQUE, btree (world_id, "tileY", "tileX") "ywot_tile_world_id" btree (world_id) And this is the query I'm trying to optimize: ywot=> EXPLAIN ANALYZE SELECT * FROM "ywot_tile" WHERE ("world_id" = 27685 AND "tileY" <= 6 AND "tileX" <= 9 AND "tileX" >= -2 AND "tileY" >= -1 ); QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------- Bitmap Heap Scan on ywot_tile (cost=11384.13..149421.27 rows=65989 width=168) (actual time=79.646..80.075 rows=96 loops=1) Recheck Cond: ((world_id = 27685) AND ("tileY" <= 6) AND ("tileY" >= (-1)) AND ("tileX" <= 9) AND ("tileX" >= (-2))) -> Bitmap Index Scan on ywot_tile_world_id_key (cost=0.00..11367.63 rows=65989 width=0) (actual time=79.615..79.615 rows=125 loops=1) Index Cond: ((world_id = 27685) AND ("tileY" <= 6) AND ("tileY" >= (-1)) AND ("tileX" <= 9) AND ("tileX" >= (-2))) Total runtime: 80.194 ms So the world is fixed, and we are querying for a rectangular region of tiles. Some more information that might be relevant: All the tiles for a queried region may or may not be present The height and width of a queried rectangle are typically about 10x10-20x20 For any given (world, X) or (world, Y) pair, there may be an unbounded number of matching tiles, but the worst case is currently around 10,000, and typically there are far fewer. New tiles are created far less frequently than existing ones are updated (changing the 'value'), and that itself is far less frequent that just reading as in the query above. The only thing I can think of would be to index on (world, X) and (world, Y). My guess is that the database would be able to take those two sets and intersect them. The problem is that there is a potentially unbounded number of matches for either for either of those. Is there some other kind of index that would be more appropriate?

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• How can I pass managed objects from one AppDomain to another?

  - by Dennis P

  I have two assemblies that I'm trying to link together. One is a sort of background process that's built with WinForms and will be designed to run as a Windows Service. I have a second project that will act as a UI for the background process whenever a user launches it. I've never tried attempting something like this with managed code before, so I've started trying to use windows messages to communicate between the two processes. I'm struggling when it comes to passing more than just IntPtrs back and forth, however. Here's the code from a control in my UI project that registers itself with the background process: public void Init() { IntPtr hwnd = IntPtr.Zero; Process[] ps = Process.GetProcessesByName("BGServiceApp"); Process mainProcess = null; if(ps == null || ps.GetLength(0) == 0) { mainProcess = LaunchApp(); } else { mainProcess = ps[0]; } SendMessage(mainProcess.MainWindowHandle, INIT_CONNECTION, this.Handle, IntPtr.Zero); } protected override void WndProc(ref Message m) { if(m.Msg == INIT_CONFIRMED && InitComplete != null) { string message = Marshal.PtrToStringAuto(m.WParam); Marshal.FreeHGlobal(m.WParam); InitComplete(message, EventArgs.Empty); } base.WndProc(ref m); } This is the code from the background process that's supposed to receive a request from the UI process to register for status updates and send a confirmation message. protected override void WndProc(ref Message m) { if(m.Msg == INIT_CONNECTION) { RegisterUIDispatcher(m.WParam); Respond(m.WParam); } if(m.Msg == UNINIT_CONNECTION) { UnregisterUIDispatcher(m.WParam); if(m_RegisteredDispatchers.Count == 0) { this.Close(); } } base.WndProc(ref m); } private void Respond(IntPtr caller) { string test = "Registration confirmed!"; IntPtr ptr = Marshal.StringToHGlobalAuto(test); SendMessage(caller, INIT_CONFIRMED, ptr, IntPtr.Zero); } } The UI process receives the INIT_CONFIRMED message from my background process, but when I try to marshal the IntPtr back into a string, I get an empty string. Is the area of heap I'm using out of scope to the other process or am I missing some security attribute maybe? Is there a better and cleaner way to go about something like this using an event driven model?

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• Different files on shared partition?

  - by Matt Robertson

  I am dual-booting Windows 8 and Ubuntu 12.04. My partition scheme looks like this: /dev/sda1 - Windows 8 (nfts) /dev/sda2 - Ubuntu / (ext4) /dev/sda3 - Ubuntu home (ext4) /dev/sda5 - swap /dev/sda6 - Shared data partition (exfat) (First off, yes I do have exfat libraries installed on Ubuntu) I created some PNG images in Windows and saved them on my shared partition. From Ubuntu, I edited the images in GIMP and saved them (replacing the ones on the shared partition). When I boot into Windows, the files appear unchanged - exactly like they did before I edited them from Ubuntu. I even added a folder and deleted some other files, but none of these changes exist in Windows. When I boot into Ubuntu, all of the changes are still there. It is as if Windows is caching the old file structure... How is this possible? Thanks in advance. Edit -- commands output ~~ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 465.8G 0 disk +-sda1 8:1 0 165.1G 0 part +-sda2 8:2 0 21.3G 0 part / +-sda3 8:3 0 98.9G 0 part /home +-sda4 8:4 0 1K 0 part +-sda5 8:5 0 7.8G 0 part [SWAP] +-sda6 8:6 0 172.7G 0 part /mnt/shared_data ~~ /etc/fstab # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 # /dev/sda2 UUID=8f700f65-b5c7-4afc-a6fb-8f9271e0fb5e / ext4 errors=remount-ro 0 1 # /dev/sda3 UUID=f0d688b7-22bd-4fa7-bc1b-a594af2933fa /home ext4 defaults 0 2 # /dev/sda5 UUID=3bc2399b-5deb-4f04-924b-d4fc77491997 none swap sw 0 0 # /dev/sda6 UUID=F2DE-BC47 /mnt/shared_data exfat defaults 0 3 ~~ /etc/mtab /dev/sda2 / ext4 rw,errors=remount-ro 0 0 proc /proc proc rw,noexec,nosuid,nodev 0 0 sysfs /sys sysfs rw,noexec,nosuid,nodev 0 0 none /sys/fs/fuse/connections fusectl rw 0 0 none /sys/kernel/debug debugfs rw 0 0 none /sys/kernel/security securityfs rw 0 0 udev /dev devtmpfs rw,mode=0755 0 0 devpts /dev/pts devpts rw,noexec,nosuid,gid=5,mode=0620 0 0 tmpfs /run tmpfs rw,noexec,nosuid,size=10%,mode=0755 0 0 none /run/lock tmpfs rw,noexec,nosuid,nodev,size=5242880 0 0 none /run/shm tmpfs rw,nosuid,nodev 0 0 /dev/sda3 /home ext4 rw 0 0 /dev/sda6 /mnt/shared_data fuseblk rw,nosuid,nodev,allow_other,blksize=4096 0 0 binfmt_misc /proc/sys/fs/binfmt_misc binfmt_misc rw,noexec,nosuid,nodev 0 0 gvfs-fuse-daemon /home/matt/.gvfs fuse.gvfs-fuse-daemon rw,nosuid,nodev,user=matt 0 0

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• Java Runtime.freeMemory() returning bizarre results when adding more objects

  - by Sotirios Delimanolis

  For whatever reason, I wanted to see how many objects I could create and populate a LinkedList with. I used Runtime.getRuntime().freeMemory() to get the approximation of free memory in my JVM. I wrote this: public static void main(String[] arg) { Scanner kb = new Scanner(System.in); List<Long> mem = new LinkedList<Long>(); while (true) { System.out.println("Max memory: " + Runtime.getRuntime().maxMemory() + ". Available memory: " + Runtime.getRuntime().freeMemory() + " bytes. Press enter to use more."); String s = kb.nextLine(); if (s.equals("m")) for (int i = 0; i < 1000000; i++) { mem.add(new Long((new Random()).nextLong())); } } } If I write in m, the app adds a million Long objects to the list. You would think the more objects (to which we have references, so can't be gc'ed), the less free memory. Running the code: Max memory: 1897725952. Available memory: 127257696 bytes. m Max memory: 1897725952. Available memory: 108426520 bytes. m Max memory: 1897725952. Available memory: 139873296 bytes. m Max memory: 1897725952. Available memory: 210632232 bytes. m Max memory: 1897725952. Available memory: 137268792 bytes. m Max memory: 1897725952. Available memory: 239504784 bytes. m Max memory: 1897725952. Available memory: 169507792 bytes. m Max memory: 1897725952. Available memory: 259686128 bytes. m Max memory: 1897725952. Available memory: 189293488 bytes. m Max memory: 1897725952. Available memory: 387686544 bytes. The available memory fluctuates. How does this happen? Is the GC cleaning up other things (what other things are there on the heap to really clean up?), is the freeMemory() method returning an approximation that's way off? Am I missing something or am I crazy?

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• Parallel.For maintain input list order on output list

  - by romeozor

  I'd like some input on keeping the order of a list during heavy-duty operations that I decided to try to do in a parallel manner to see if it boosts performance. (It did!) I came up with a solution, but since this was my first attempt at anything parallel, I'd need someone to slap my hands if I did something very stupid. There's a query that returns a list of card owners, sorted by name, then by date of birth. This needs to be rendered in a table on a web page (ASP.Net WebForms). The original coder decided he would construct the table cell-by-cell (TableCell), add them to rows (TableRow), then each row to the table. So no GridView, allegedly its performance is bad, but the performance was very poor regardless :). The database query returns in no time, the most time is spent on looping through the results and adding table cells etc. I made the following method to maintain the original order of the list: private TableRow[] ComposeRows(List<CardHolder> queryResult) { int queryElementsCount = queryResult.Count(); // array with the query's size var rowArray = new TableRow[queryElementsCount]; Parallel.For(0, queryElementsCount, i => { var row = new TableRow(); var cell = new TableCell(); // various operations, including simple ones such as: cell.Text = queryResult[i].Name; row.Cells.Add(cell); // here I'm adding the current item to it's original index // to maintain order in the output list rowArray[i] = row; }); return rowArray; } So as you can see, because I'm returning a very different type of data (List<CardHolder> -> TableRow[]), I can't just simply omit the ordering from the original query to do it after the operations. Also, I also thought it would be a good idea to Dispose() the objects at the end of each loop, because the query can return a huge list and letting cell and row objects pile up in the heap could impact performance.(?) How badly did I do? Does anyone have a better solution in case mine is flawed?

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