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  • Tomcat memory issue

    - by user305210
    Hello, I have noticed that my application that is running on Tomcat 5 starts with 1gig of memory and as soon as it starts receiving requests from client, the memory starts dropping until it is down to 100MBs and troubles start from there. I am looking at /manager/status page of tomcat under JVM section where "Free Memory", "Total Memory", "Max Memory" is listed. Is this an indicator of memory leak? Memory does not seem to be freed-up automatically even if there are no requests coming from client machines.

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  • Page Fault Interrupt Problems

    - by Vikas
    This is a statement referring to problem caused by page fault:(from Silberschatz 7th ed P-310 last para) 'We cant simply restart instructions when instruction modifies several different location Ex:when a instruction moves 256 bytes from source to dest and either src or dest straddles on page boundary , then,after a partial move, if a page fault occurs, 'we can't simply restart the instructions' My question is Why not? Simply restart the instruction again do the same copy after page is in. Is there any problem in it?

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  • Condition Variable in Shared Memory - is this code POSIX-conformant?

    - by GrahamS
    We've been trying to use a mutex and condition variable to synchronise access to named shared memory on a LynuxWorks LynxOS-SE system (POSIX-conformant). One shared memory block is called "/sync" and contains the mutex and condition variable, the other is "/data" and contains the actual data we are syncing access to. We're seeing failures from pthread_cond_signal() if both processes don't perform the mmap() calls in exactly the same order, or if one process mmaps in some other piece of shared memory before it mmaps the sync memory. This example code is about as short as I can make it: #include <sys/types.h> #include <sys/stat.h> #include <sys/mman.h> #include <sys/file.h> #include <stdlib.h> #include <pthread.h> #include <errno.h> #include <iostream> #include <string> using namespace std; static const string shm_name_sync("/sync"); static const string shm_name_data("/data"); struct shared_memory_sync { pthread_mutex_t mutex; pthread_cond_t condition; }; struct shared_memory_data { int a; int b; }; //Create 2 shared memory objects // - sync contains 2 shared synchronisation objects (mutex and condition) // - data not important void create() { // Create and map 'sync' shared memory int fd_sync = shm_open(shm_name_sync.c_str(), O_CREAT|O_RDWR, S_IRUSR|S_IWUSR); ftruncate(fd_sync, sizeof(shared_memory_sync)); void* addr_sync = mmap(0, sizeof(shared_memory_sync), PROT_READ|PROT_WRITE, MAP_SHARED, fd_sync, 0); shared_memory_sync* p_sync = static_cast<shared_memory_sync*> (addr_sync); // init the cond and mutex pthread_condattr_t cond_attr; pthread_condattr_init(&cond_attr); pthread_condattr_setpshared(&cond_attr, PTHREAD_PROCESS_SHARED); pthread_cond_init(&(p_sync->condition), &cond_attr); pthread_condattr_destroy(&cond_attr); pthread_mutexattr_t m_attr; pthread_mutexattr_init(&m_attr); pthread_mutexattr_setpshared(&m_attr, PTHREAD_PROCESS_SHARED); pthread_mutex_init(&(p_sync->mutex), &m_attr); pthread_mutexattr_destroy(&m_attr); // Create the 'data' shared memory int fd_data = shm_open(shm_name_data.c_str(), O_CREAT|O_RDWR, S_IRUSR|S_IWUSR); ftruncate(fd_data, sizeof(shared_memory_data)); void* addr_data = mmap(0, sizeof(shared_memory_data), PROT_READ|PROT_WRITE, MAP_SHARED, fd_data, 0); shared_memory_data* p_data = static_cast<shared_memory_data*> (addr_data); // Run the second process while it sleeps here. sleep(10); int res = pthread_cond_signal(&(p_sync->condition)); assert(res==0); // <--- !!!THIS ASSERT WILL FAIL ON LYNXOS!!! munmap(addr_sync, sizeof(shared_memory_sync)); shm_unlink(shm_name_sync.c_str()); munmap(addr_data, sizeof(shared_memory_data)); shm_unlink(shm_name_data.c_str()); } //Open the same 2 shared memory objects but in reverse order // - data // - sync void open() { sleep(2); int fd_data = shm_open(shm_name_data.c_str(), O_RDWR, S_IRUSR|S_IWUSR); void* addr_data = mmap(0, sizeof(shared_memory_data), PROT_READ|PROT_WRITE, MAP_SHARED, fd_data, 0); shared_memory_data* p_data = static_cast<shared_memory_data*> (addr_data); int fd_sync = shm_open(shm_name_sync.c_str(), O_RDWR, S_IRUSR|S_IWUSR); void* addr_sync = mmap(0, sizeof(shared_memory_sync), PROT_READ|PROT_WRITE, MAP_SHARED, fd_sync, 0); shared_memory_sync* p_sync = static_cast<shared_memory_sync*> (addr_sync); // Wait on the condvar pthread_mutex_lock(&(p_sync->mutex)); pthread_cond_wait(&(p_sync->condition), &(p_sync->mutex)); pthread_mutex_unlock(&(p_sync->mutex)); munmap(addr_sync, sizeof(shared_memory_sync)); munmap(addr_data, sizeof(shared_memory_data)); } int main(int argc, char** argv) { if(argc>1) { open(); } else { create(); } return (0); } Run this program with no args, then another copy with args, and the first one will fail at the assert checking the pthread_cond_signal(). But change the open() function to mmap() the "/sync" memory first and it will all work fine. This seems like a major bug in LynxOS but LynuxWorks claim that using mutex and condition variable in this way is not covered by the POSIX standard, so they are not interested. Can anyone determine if this code does violate POSIX? Or does anyone have any convincing documentation that it is POSIX compliant?

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  • System says memory controller not available and doesn't boot?

    - by Martin
    Hello everybody, Recently I have had a MainBoard-problem. I've send my mainboard to service and today I got it back from the company. It is a Foxconn 520a mainboard. Now I have installed my exchanged mainboard. But now I have a problem. My system boots until the device list with IRQ entries appear. The system says "Verifying DMI-pool-data..." and nothing happens. The IRQ-device list shows that the memory-controller is not available. All other devices have got an IRQ. Bus No. Device No. Func No. Vendor/Device Class Device Class IRQ 0 0 0 10DE 0547 0500 Memory Controller NA Do you have any ideas where the problem could be? I already have disconnected all unnecessary devices like the hard disks. Perhaps it is a BIOS problem, but I don't know where I should look. Would be nice if there is any advice, Greetings, Martin

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  • Installed 4GB memory but Windows XP 32 bit only reporting 2GB?

    - by AnthonyWJones
    I've just taken an existing XP Pro 32 bit system that had only 0.5GB of memory installed and maxed it out to 4GB. The BIOS reports the 4GB ram however when XP is booted and I look at the computer properties only 2GB of RAM is reported. Can anyone explain this? Before we go up any blind allys the /3GB switch is not the answer here, I have no need for a single process to use more the 2GB of memory. I'm wondering if the the 32 bit XP Pro is deliberately limited to 2GB. I seem to remember seeing an excellent table on a Microsoft site listing all the various SKUs of Windows and what each one was limited to. However I can't seem to find that table now.

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  • Installed 4GB memory but Windows XP 32 bit only reporting 2GB?

    - by AnthonyWJones
    I've just taken an existing XP Pro 32 bit system that had only 0.5GB of memory installed and maxed it out to 4GB. The BIOS reports the 4GB ram however when XP is booted and I look at the computer properties only 2GB of RAM is reported. Can anyone explain this? Before we go up any blind allys the /3GB switch is not the answer here, I have no need for a single process to use more the 2GB of memory. I'm wondering if the the 32 bit XP Pro is deliberately limited to 2GB. I seem to remember seeing an excellent table on a Microsoft site listing all the various SKUs of Windows and what each one was limited to. However I can't seem to find that table now.

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  • Per bytes RAM memory acess

    - by b-gen-jack-o-neill
    Hi, I have just a simple question. Today memory DDR chips are 64 bits wide, and the CPU data bus is also 64 bits wide. But memory is stil organised in single bytes. So, what I want to ask is, when CPU selects some memory adress, it should be one byte, right? Becouse the lowest memory portion you can access is 1 byte. But, if you get 1 byte per 1 adress, why is memory bus 8 bytes wide?

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  • Memory management (segmentation and paging) in 80286 and 80386: How does it work?

    - by Andrew J. Brehm
    I found lots of Web sites and books explaining how memory management worked on the 8086 and later x86 CPUs in Real Mode. I understand, I think, how two 16 bit values, segment address and offset are combined to get a linear 20 bit physical address (shift segment four bits to the left, add offset; segments are 64K and start every 16 bytes). But I couldn't find any good Web sites or books that explained how memory management works in Protected Mode, specifically the differences between 80286 and 80386. Can anyone point me to a good Web site or book (or explain it right here)? (For extra credit, i.e. an upvote, how does it work in Long Mode?)

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  • How do I make the Windows low memory warning less sensitive?

    - by Stephen
    I keep getting this annoying low memory warning/prompt to close games I play. It happens very often and I still have ~6 gigs of ram free. I disabled virtual memory because it was putting stuff on the pagefile when I had 10 gigs free ram so that spiked my disk usage. Is there any way to disable this warning? I have 16GB ram so it shouldn't be an issue. I would prefer to keep pagefiles off because my HD is very loud so it's nice to keep it spun down as much as possible. I don't want to disable it completely. Ideally, I would like it to go off when I have ~2GB left rather than 6, but if this isn't viable, I may just disable it completely.

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  • ideal memory configuration 4 bank, ddr3, AM3+ FX - 1 vs 2 vs 4 dimms?

    - by TardisGuy
    Ok, so ive been looking around, trying to learn and understand the way that ram works. Ive gotten one answer that said "The addressing is best for 2 sticks, and when you use 4; it slows down" Another answer said something like: Theres bank/channel interleave that makes the memory read like one stick Also I read something about the memory density also being a factor. I dug further and found out that theres a higher speed limit on my board for 2 sticks vs 4, so now im trying to put an image in my head of how and why, and... pfft. Can anyone explain, or recommend a resource that would answer these questions?

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  • Do memory cards have any max file size limitation?

    - by Dmitriy R
    I am not sure where to ask this question, so perhaps it is physical limitation. I have a 8 GB flash micro SD memory card. When I copy any file size of up to few gigabytes, copying happens normally. But if I am trying to copy file over 4 GB file, then the system tells me like insufficient memory on card, although 8 GB is available. So perhaps only 32 bit address is used for keeping size of file in micro SD card, or is my micro SD defective?

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  • 2 GB of memory in 1 GB system is a problem?

    - by daveslab
    Hi folks, I just installed 2 1 Gig sticks into my friend's machine, thinking that it would take all the 2 GBs. Unfortunately, according to Dell's website, it says the maximum amount of memory accessible to the machine is arbitrarily set to 1 GB! The system indeed reports having 1 GB of memory accessible to it, but I'm worried that having 2 GB in there might break something. Are my fears reasonable? Should I buy two 512 MB sticks instead? Thanks for any help!

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  • Is it safe to use up all memory on linux server, not leaving anything for the cache?

    - by Temnovit
    I have a CentOS server fully dedicated to MySQL 5.5 (with innodb tables mostly). Server has 32 GB RAM, SSD disks, and avarage memory usage looks like this: So about 25GB is in use and about 6.5GB is cached. I am experiencing performance problems with WRITE queries, so I was thinking, is this the optimal cache size? I might increase innodb buffer size, so that linux cache would become smaller, or decrease it, so it would be bigger. What is the optimal used/cached memory balance for busy MySQL server on linux?

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  • We have a Solaris 9 server running Oracle 10G and have been getting memory consumption errors for a few weeks now

    - by another_netadmin
    We recently upgraded our Enterprise application and everything worked ok until one weekend when we did a server reboot, ever since then we have run into memory errors. The server has 4GB of physical memory installed and the kernel parameters are set to the following (/etc/system). I'm not an Oracle guy so I'm not sure where to start looking but any informaiton is greatly appreciated. Thanks in advance. There are two databases running on this server, one is a production database and the other is a pre-production database. [root@bandb /]# cat /etc/system | grep seminfo set semsys:seminfo_semmni=100 set semsys:seminfo_semmns=2048 set semsys:seminfo_semmsl=400 set semsys:seminfo_semopm=100 set semsys:seminfo_semvmx=32767 [root@bandb /]# cat /etc/system | grep shminfo set shmsys:shminfo_shmmax=4294967295 set shmsys:shminfo_shmmin=1 set shmsys:shminfo_shmmni=100 set shmsys:shminfo_shmseg=10 [root@bandb /]#

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  • PASS 13 Dispatches: Memory Optimized = On

    - by Tony Davis
    I'm at the PASS Summit in Charlotte for the Day 1 keynote by Quentin Clarke, Corporate VP of the data platform group at Microsoft. He's talking about how SQL Server 2014 is “pushing boundaries” and first up is SQL Server 2014's In-Memory OLTP technology (former codename “hekaton”) It is a feature that provokes a lot of interest and for good reason as, without any need for application rewrites or hardware updates, it can enable us to ensure that an application can find in memory most or all of the data it needs, and can lead to huge improvements in processing times. A good recent hekaton use cases article talks about applications that need a “Shock Absorber” when either spikes or just a high rate of incoming workload (including data in ETL scenarios) become a primary bottleneck. To get a really deep look at this technology, I would check out David DeWitt's summit keynote tomorrow (it will be live streamed). Other than that, to get started I'd recommend Kalen Delaney's whitepaper. She offers a lot of insight into how it works and how to start to define memory-optimized tables, and natively compiled stored procedures. These memory-optimized tables uses completely optimistic multi-version concurrency control – no waiting on locks! After that, Tom LaRock has compiled a useful set of links to drill deeper, and includes one to Microsoft's AMR tool to help you gauge the tables that might benefit most. Tony.

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  • Memory concerns while plotting escape from DLL Hell in Delphi

    - by Peter Turner
    I work on a program with about 50 DLLs that are loaded from one executable, it's an old organically grown program where the only rationale for creating a new DLL is that one previously didn't exist to fill a given need. (and namespaces didn't exist in Delphi so it never crossed our mind to make dll1.main.pas, dll2.main.pas or something even more unique) What we want to do is consolidate all these DLLs into one executable, since none of them are used out of the program, there shouldn't be much of a problem. The concern my boss has is that if we did this, the memory overhead for terminal server clients would go through the roof. So, I've stepped through enough initialization code to know that lots of stuff is done every time a DLL is loaded in to memory, but say I've got a project with about 4000 files, and 50 dlls, 10 of which are probably utilized by any one user in any one session of the program. The 50 dlls are about 2/3rds form files, if not more, but beyond that there's not a lot of other resources being loaded (only a few embedded pictures, icons, cursors, etc..). If I loaded all these files in to memory, how much memory is used per unit? how much is used per class? How do I keep the overhead down? and what is the biggest project one can reasonably expect to build with Delphi? This tidbit won't help answering, but I think it might clarify what my boss is worried about, we currently start our program at about 18megs, normal working conditions are usually less than 40 megs, he thinks it could climb as high as 120 megs.

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  • Understanding how memory contents map into a struct

    - by user95592
    I am not able to understand how bytes in memory are being mapped into a struct. My machine is a little-endian x86_64. The code was compiled with gcc 4.7.0 from the Win64 mingw32-64 distribution for Win64. These are contents of the relevant memory fragment: ...450002cf9fe5000040115a9fc0a8fe... And this is the struct definition: typedef struct ip4 { unsigned int ihl :4; unsigned int version :4; uint8_t tos; uint16_t tot_len; uint16_t id; uint16_t frag_off; // flags=3 bits, offset=13 bits uint8_t ttl; uint8_t protocol; uint16_t check; uint32_t saddr; uint32_t daddr; /*The options start here. */ } ip4_t; When a pointer to such an structure (let it be *ip4) is initialized to the starting address of the above pasted memory region, this is what the debugger shows for the struct's fields: ip4: address=0x8da36ce ip4->ihl: address=0x8da36ce, value=0x5 ip4->version: address=0x8da36ce, value=0x4 ip4->tos: address=0x8da36d2, value=0x9f ip4->tot_len: address=0x8da36d4, value=0x0 ... I see how ihl and version are mapped: 4 bytes for a long integer, little-endian. But I don't understand how tos and tot_len are mapped; which bytes in memory correspond to each one of them. Thank you in advance.

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  • TXPAUSE : polite waiting for hardware transactional memory

    - by Dave
    Classic locks are an appropriate tool to prevent potentially conflicting operations A and B, invoked by different threads, from running at the same time. In a sense the locks cause either A to run before B or vice-versa. Similarly, we can replace the locks with hardware transactional memory, or use transactional lock elision to leverage potential disjoint access parallelism between A and B. But often we want A to wait until B has run. In a Pthreads environment we'd usually use locks in conjunction with condition variables to implement our "wait until" constraint. MONITOR-MWAIT is another way to wait for a memory location to change, but it only allows us to track one cache line and it's only available on x86. There's no similar "wait until" construct for hardware transactions. At the instruction-set level a simple way to express "wait until" in transactions would be to add a new TXPAUSE instruction that could be used within an active hardware transaction. TXPAUSE would politely stall the invoking thread, possibly surrendering or yielding compute resources, while at the same time continuing to track the transaction's address-set. Once a transaction has executed TXPAUSE it can only abort. Ideally that'd happen when some other thread modifies a variable that's in the transaction's read-set or write-set. And since we're aborting all writes would be discarded. In a sense this gives us multi-location MWAIT but with much more flexibility. We could also augment the TXPAUSE with a cycle-count bound to cap the time spent stalled. I should note that we can already enter a tight spin loop in a transaction to wait for updates to address-set to cause an abort. Assuming that the implementation monitors the address-set via cache-coherence probes, by waiting in this fashion we actually communicate via the probes, and not via memory values. That is the updating thread signals the waiter via probes instead of by traditional memory values. But TXPAUSE gives us a polite way to spin.

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  • What is a good metaphor for c memory management?

    - by fsmc
    I'm trying to find a good metaphor to explain memory allocation, initialization and freeing in c to a non technical audience. I've heard pass-by-reference/value talked about quite well with postal service usage, but not so much for allocation/deallocation. So for I've thought about using the idea of renting a space might work, but I wonder if the SO crew can provide something better.

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  • [PHP] - Lowering script memory usage in a "big" file creation

    - by Riccardo
    Hi there people, it looks like I'm facing a typical memory outage problem when using a PHP script. The script, originally developed by another person, serves as an XML sitemap creator, and on large websites uses quite a lot of memory. I thought that the problem was related due to an algorithm holding data in memory until the job was done, but digging into the code I have discovered that the script works in this way: open file in output (will contain XML sitemap entries) in the loop: ---- for each entry to be added in sitemap, do fwrite close file end Although there are no huge arrays or variables being kept in memory, this technique uses a lot of memory. I thought that maybe PHP was buffering under the hood the fwrites and "flushing" data at the end of the script, so I have modified the code to close and open the file every Nth record, but the memory usage is still the same.... I'm debugging the script on my computer and watching memory usage: while script execution runs, memory allocation grows. Is there a particular technique to instruct PHP to free unsed memory, to force flushing buffers if any? Thanks

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