Search Results

Search found 12267 results on 491 pages for 'out of memory'.

Page 166/491 | < Previous Page | 162 163 164 165 166 167 168 169 170 171 172 173  | Next Page >

• Atheros Wireless card shows up as two different models?

  - by geermc4

  Hi I've been fighting these wireless drivers for a few days and just recently i noticed that the model the Wireless controller appears in lspci is different sometimes. This is the data i have after installing Ubuntu Server 64 bit ~# lspci -k .... 04:00.0 Network controller: Atheros Communications Inc. AR9285 Wireless Network Adapter (PCI-Express) (rev 01) Subsystem: AzureWave Device 1d89 Kernel driver in use: ath9k Kernel modules: ath9k ran some updates, restarted, all was good, all though it did say that linux-headers-server linux-image-server linux-server where beeing kept back. After that i installed ubuntu-desktop (aptitude install ubuntu-desktop --without-recommends) restarted and not only is the wireless not working anymore, but the hardware is listed as a different card ~# lspci -k .... 04:00.0 Ethernet controller: Atheros Communications Inc. AR5008 Wireless Network Adapter (rev 01) has no available drivers for it, still i tried to modprobe ath9k, they show up in lsmod as loaded, but still iw list shows nothing. this is what it looked like before the ubuntu-desktop instalation Wiphy phy0 Band 1: Capabilities: 0x11ce HT20/HT40 SM Power Save disabled RX HT40 SGI TX STBC RX STBC 1-stream Max AMSDU length: 3839 bytes DSSS/CCK HT40 Maximum RX AMPDU length 65535 bytes (exponent: 0x003) Minimum RX AMPDU time spacing: 8 usec (0x06) HT TX/RX MCS rate indexes supported: 0-7 Frequencies: * 2412 MHz [1] (14.0 dBm) * 2417 MHz [2] (15.0 dBm) * 2422 MHz [3] (15.0 dBm) * 2427 MHz [4] (15.0 dBm) * 2432 MHz [5] (15.0 dBm) * 2437 MHz [6] (15.0 dBm) * 2442 MHz [7] (15.0 dBm) * 2447 MHz [8] (15.0 dBm) * 2452 MHz [9] (15.0 dBm) * 2457 MHz [10] (15.0 dBm) * 2462 MHz [11] (15.0 dBm) * 2467 MHz [12] (15.0 dBm) (passive scanning) * 2472 MHz [13] (14.0 dBm) (passive scanning) * 2484 MHz [14] (17.0 dBm) (passive scanning) Bitrates (non-HT): * 1.0 Mbps * 2.0 Mbps (short preamble supported) * 5.5 Mbps (short preamble supported) * 11.0 Mbps (short preamble supported) * 6.0 Mbps * 9.0 Mbps * 12.0 Mbps * 18.0 Mbps * 24.0 Mbps * 36.0 Mbps * 48.0 Mbps * 54.0 Mbps max # scan SSIDs: 4 max scan IEs length: 2257 bytes Coverage class: 0 (up to 0m) Supported Ciphers: * WEP40 (00-0f-ac:1) * WEP104 (00-0f-ac:5) * TKIP (00-0f-ac:2) * CCMP (00-0f-ac:4) * CMAC (00-0f-ac:6) Available Antennas: TX 0x1 RX 0x3 Configured Antennas: TX 0x1 RX 0x3 Supported interface modes: * IBSS * managed * AP * AP/VLAN * WDS * monitor * mesh point * P2P-client * P2P-GO software interface modes (can always be added): * AP/VLAN * monitor interface combinations are not supported Supported commands: * new_interface * set_interface * new_key * new_beacon * new_station * new_mpath * set_mesh_params * set_bss * authenticate * associate * deauthenticate * disassociate * join_ibss * join_mesh * remain_on_channel * set_tx_bitrate_mask * action * frame_wait_cancel * set_wiphy_netns * set_channel * set_wds_peer * connect * disconnect Supported TX frame types: * IBSS: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 * managed: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 * AP: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 * AP/VLAN: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 * mesh point: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 * P2P-client: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 * P2P-GO: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 Supported RX frame types: * IBSS: 0x00d0 * managed: 0x0040 0x00d0 * AP: 0x0000 0x0020 0x0040 0x00a0 0x00b0 0x00c0 0x00d0 * AP/VLAN: 0x0000 0x0020 0x0040 0x00a0 0x00b0 0x00c0 0x00d0 * mesh point: 0x00b0 0x00c0 0x00d0 * P2P-client: 0x0040 0x00d0 * P2P-GO: 0x0000 0x0020 0x0040 0x00a0 0x00b0 0x00c0 0x00d0 Device supports RSN-IBSS. What's with the hardware change? If it has 2, how can i make the AR9285 always load and disable AR5008, or, is it the same and it's just showing it different? :| Oh and I've tried this on Ubuntu 10.04 server, xubuntu 12.04, ubuntu 12.04 desktop and server. Thanks in advanced. -- Here's some more info, i have it setup in 2 hard drives, 1 works and the other one i'm using to figure it out The one that works... # lshw -class network *-network description: Ethernet interface product: RTL8111/8168B PCI Express Gigabit Ethernet controller vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: pci@0000:03:00.0 logical name: eth0 version: 06 serial: 54:04:a6:a3:3b:96 size: 1Gbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl_nic/rtl8168e-2.fw ip=192.168.2.147 latency=0 link=yes multicast=yes port=MII speed=1Gbit/s resources: irq:43 ioport:e000(size=256) memory:d0004000-d0004fff memory:d0000000-d0003fff *-network description: Wireless interface product: AR9285 Wireless Network Adapter (PCI-Express) vendor: Atheros Communications Inc. physical id: 0 bus info: pci@0000:04:00.0 logical name: wlan0 version: 01 serial: 74:2f:68:4a:26:73 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=ath9k driverversion=3.2.0-18-generic-pae firmware=N/A latency=0 link=no multicast=yes wireless=IEEE 802.11bgn resources: irq:18 memory:fea00000-fea0ffff Here's where it doesn't # lshw -class network *-network description: Ethernet interface product: RTL8111/8168B PCI Express Gigabit Ethernet controller vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: pci@0000:03:00.0 logical name: eth0 version: 06 serial: 54:04:a6:a3:3b:96 size: 1Gbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl_nic/rtl8168e-2.fw ip=192.168.2.160 latency=0 link=yes multicast=yes port=MII speed=1Gbit/s resources: irq:43 ioport:e000(size=256) memory:d0004000-d0004fff memory:d0000000-d0003fff *-network UNCLAIMED description: Ethernet controller product: AR5008 Wireless Network Adapter vendor: Atheros Communications Inc. physical id: 0 bus info: pci@0000:04:00.0 version: 01 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list configuration: latency=0 resources: memory:fea00000-fea0ffff Update I've noticed that if i blacklist the ath9k and ath9k_common modules lspci gives me the AR9285, but then I need to modprobe ath9k for it to work, does this make any sense? If so, why?

  Read the article

• How to install Intel VGA drive..?

  - by Ary Catur Wicaksono

  how to install intel VGA drive..?? I've been searching on google but did not see too I've been trying to ask the ubuntu forum in Indonesia. but they did not reply my post.. is there anything that can help me? *I am sorry my English is rather chaotic arthur@Chunx:~$ lspci | grep VGA 00:02.0 VGA compatible controller: Intel Corporation 82G33/G31 Express Integrated Graphics Controller (rev 10) arthur@Chunx:~$ sudo lshw -c display [sudo] password for arthur: *-display description: VGA compatible controller product: 82G33/G31 Express Integrated Graphics Controller vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 version: 10 width: 32 bits clock: 33MHz capabilities: msi pm vga_controller bus_master cap_list rom configuration: driver=i915 latency=0 resources: irq:42 memory:fea80000-feafffff ioport:dc00(size=8) memory:e0000000-efffffff memory:fe900000-fe9fffff arthur@Chunx:~$ sudo apt-get install xserver-xorg-video-intel Sedang membaca daftar paket... Selesai Membangun pohon ketergantungan Membaca informasi yang tersedia... Selesai xserver-xorg-video-intel telah berada dalam versi terbaru. 0 dimutakhirkan, 0 baru terinstal, 0 akan dihapus dan 190 tidak akan dimutakhirkan.

  Read the article

• Can't connect to WIFI after sleep Ubuntu 14.04

  - by user3380404

  After an upgrade over a previous version to Ubuntu 14.04 I have problems with connecting to WiFi. After suspending it won't reconnect to any existing network unless I restart the laptop. sudo lshw -C network: *-network description: Ethernet interface product: 82567LM Gigabit Network Connection vendor: Intel Corporation physical id: 19 bus info: pci@0000:00:19.0 logical name: eth0 version: 03 serial: 00:27:13:b4:d3:58 capacity: 1Gbit/s width: 32 bits clock: 33MHz capabilities: pm msi bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=e1000e driverversion=2.3.2-k firmware=1.8-3 latency=0 link=no multicast=yes port=twisted pair resources: irq:45 memory:fc200000-fc21ffff memory:fc225000-fc225fff ioport:1840(size=32) *-network description: Wireless interface product: PRO/Wireless 5100 AGN [Shiloh] Network Connection vendor: Intel Corporation physical id: 0 bus info: pci@0000:03:00.0 logical name: wlan0 version: 00 serial: 00:26:c6:c6:6b:c8 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=iwlwifi driverversion=3.13.0-29-generic firmware=8.83.5.1 build 33692 ip=10.0.1.160 latency=0 link=yes multicast=yes wireless=IEEE 802.11abgn resources: irq:48 memory:f4200000-f4201fff

  Read the article

• FlasCC requirements and limitations?

  - by Arthur Wulf White

  It is now available for download. It says you need twice* as many bits as I have. Why would you need more bits to compile code? Does that mean you need more bits to run flash games writtes with flasCC Did anyone try it out and happens to know the answers? http://gaming.adobe.com/technologies/flascc/ Minimum system requirements Flash Player 11 or higher Flex SDK 4.6 or higher Java Virtual Machine (64-bit) Windows Microsoft® Windows® 7 (64-bit edition) Cygwin (included) *This is meant as a joke. however I do own a 32-bit laptop and I am wondering why you need 64-bit. Afaik - You only need 64-bit if you want to run a system that has more than 4gigs of memory. Why would any flash game require more than 4 gigs of memory. The only system that is 64-bits and does not have 4gigs of memory that I can quickly recall is that hilarious Nintendo that came ages ago with a Motorola CPU.

  Read the article

• Crashing trying to install Ubuntu 12.04 LTS

  - by Daniel Evans

  Hardware: Dell Inspiron 1545 Steps are as follows: 1. Insert 64 bit Ubuntu 12.04 disc 2. Boot computer Output is as follows: error: unexpectedly disconnected from boot status daemon Generating locales... en_US.UTF-8... done Generation complete. MEMORY-ERROR: glib-compile-schemas[569]: GSlice: assertion failed: aligned_memory == (gpointer) addr Aborted pwconv: failed to change the mode of /etc/passwd- to 0600 MEMORY-ERROR: [996]: GSlice: assertion failed: aligned_memory == (gpointer) addr MEMORY-ERROR: glib-compile-scehmas[1034]: GSlice: assertion failed: aligned_memory == gpointer) addr Aborted /usr/lib/python2.7/dist-packages/LanguageSelector/LocaleInfo.py:256: UserWarning: Failed to connect to socket /var/run/dbus/system_bus_socket: No such file or directory warnings.warn(msg.args[0].encode('UTF-8')) Using CD-ROM mount point /cdrom ... etc etc... End up at a prompt line ubuntu@ubuntu:~$

  Read the article

• What is a safe ulimit ceiling?

  - by Kaustubh P

  This is the output of ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 16382 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) unlimited virtual memory (kbytes, -v) unlimited file locks (-x) unlimited This is a 64bit install, and I would like to increase the max-open files from 1024 to a more heady limit such as 5000. Will that be any problem? Will it cause instability? Thanks.

  Read the article

• Ubuntu 14.04 doesn't detect my discrete GPU

  - by user258887

  I recently purchased a laptop with an Nvidia GeForce 860m, and have installed Ubuntu 14.04. On my old laptop I had 12.04, which automatically filled Additional Drivers with Nvidia drivers. But on this computer, the only thing in Additional Drivers is Qualcomm. So I manually installed Nvidia, but X Server Settings doesn't seem to detect any GPU... lspci | grep VGA reports only my integrated Intel GPU, but lspci -v reports many things, including the Nvidia GPU: 01:00.0 3D controller: NVIDIA Corporation GM107M [GeForce GTX 860M] (rev a2) Subsystem: ASUSTeK Computer Inc. Device 157d Flags: fast devsel, IRQ 16 Memory at ec000000 (32-bit, non-prefetchable) [size=16M] Memory at c0000000 (64-bit, prefetchable) [size=256M] Memory at d0000000 (64-bit, prefetchable) [size=32M] I/O ports at e000 [size=128] Expansion ROM at ed000000 [disabled] [size=512K] Capabilities: access denied Don't know what any of that means. Not sure if it's supposed to say 'access denied'... I need my GPU to do CUDA and OpenGL programming. What else can I do to figure out why this isn't working?

  Read the article

• Is there a size limit when using UICollectionView as tiled map for iOS game?

  - by Alexander Winn

  I'm working on a turn-based strategy game for iOS, (picture Civilization 2 as an example), and I'm considering using a UICollectionView as my game map. Each cell would be a tile, and I could use the "didSelectCell" method to handle player interaction with each tile. Here's my question: I know that UICollectionViewCells are dequeued and reused by the OS, so does that mean that the map could support an effectively infinitely-large map, so long as only a few cells are onscreen at a time? However many cells were onscreen would be held in memory, and obviously the data source would take up some memory, but would my offscreen map be limited to a certain size or could it be enormous so long as the number of cells visible at any one time wasn't too much for the device to handle? Basically, is there any memory weight to offscreen cells, or do only visible cells have any impact?

  Read the article

• How to use unused space in ubuntu

  - by Ravi.Kumar

  I installed ubuntu on my machine with only 80 GB of memory anticipating that I will remove it later but now I want to keep it forever (until I am frustrated with linux). I have 500 GB in my machine and now I want to use that raw 420 GB of space. How I can I do that ? with "space/memory" I am referring to secondary memory not Ram. Here is output of : sudo fdisk -l Disk /dev/sda: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000dcb77 Device Boot Start End Blocks Id System /dev/sda1 * 2048 136718335 68358144 83 Linux

  Read the article

• PHP, when to use iterators, how to buffer results?

  - by Jon L.

  When is it best to use Iterators in PHP, and how can they be implemented to best avoid loading all objects into memory simultaneously? Do any constructs exist in PHP so that we can queue up results of an operation for use with an Iterator, while again avoiding loading all objects into memory simultaneously? An example would be a curl HTTP request against a REST server In the case of an HTTP request that returns all results at once (a la curl), would we be better off to go with streaming results, and if so, are there any limitations or pitfalls to be aware of? If using streaming, is it better to replace curl with a PHP native stream/socket? My intention is to implement Iterators for a REST client, and separately a document ORM that I'm maintaining, but only if I can do so while gaining benefits from reduced memory usage, increased performance, etc. Thanks in advance for any responses :-)

  Read the article

• Acer Extensa 5620 - Graphic unknown!

  - by Nycxzon

  I install Ubuntu 12.04 Beta 2, I found out the my graphic driver is "Unknown" and experience is "Standard". Please help me know how to install my graphic driver. as per my laptop specs: Mobile Intel GM965 Express Chipset with integrated 3D graphics, featuring Intel Graphics Media Accelerator (GMA) X3100 with up to 358/3845 MB of Intel Dynamic Video Memory Technology 4.0 (8 MB of dedicated system memory, up to 350/3765 MB of shared system memory), supporting Microsoft DirectX 9. Hope you can help me! Thanks in advance! Noob @ Ubuntu :) Updates! ______________ I found a solution! I found a site where I ask how to check the graphic of my system. by using terminal command "glxinfo" command ask me to install mesa-utils! and update. After that, My graphic driver is listed! Thanks for your continues support! :)

  Read the article

• Issue with text in a Intel 82945G Express Chipset Family

  - by user34681

  I am on Ubuntu 11.04 and the text in all the applications often looks with visual artifacts. I have installed xserver-xorg-video-intel. Attached a image so you can appreciate. lshw -c video output: *-display description: VGA compatible controller product: 82945G/GZ Integrated Graphics Controller vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 version: 02 width: 32 bits clock: 33MHz capabilities: msi pm vga_controller bus_master cap_list rom configuration: driver=i915 latency=0 resources: irq:16 memory:dfe00000-dfe7ffff ioport:8800(size=8) memory:e0000000-efffffff memory:dfe80000-dfebffff In the text selected in green you can see the 'Online', 'File' and 'hassle' words cut.

  Read the article

• Is it possible to update my graphic card drivers?

  - by madmaxpt

  This is what the lspci -v command shows in the VGA compatible controller section: 00:02.0 VGA compatible controller: Intel Corporation Atom Processor D4xx/D5xx/N4xx/N5xx Integrated Graphics Controller (prog-if 00 [VGA controller]) Subsystem: Dell Device 048e Flags: bus master, fast devsel, latency 0, IRQ 44 Memory at f0200000 (32-bit, non-prefetchable) [size=512K] I/O ports at 18d0 [size=8] Memory at d0000000 (32-bit, prefetchable) [size=256M] Memory at f0000000 (32-bit, non-prefetchable) [size=1M] Expansion ROM at <unassigned> [disabled] Capabilities: <access denied> Kernel driver in use: i915 Kernel modules: i915 i915 is only compatible with OpenGL 1.4 and cannot use shaders and I'd like to use some Open GL 2.0 functionalities. Is it possible to update the drivers or is my hardware limited to OpenGL 1.4 ?

  Read the article

• Distorted text in programs

  - by Teneff

  I've installed Ubuntu 11 with gnome and in some point the text in the programs becomes unreadable like this. It's not only the text, but even the desktop background looks awful. I've tried to add section in xorg.conf, but it didn't helped out. Section "Device" Identifier "g33/X3000" Driver "intel" BusID "PCI:0:2:0" Option "ModeDebug" "on" Option "MonitorLayout" "LCD,VGA" Option "DevicePresence" "true" EndSection And this is what the lshw returns about the VGA *-display description: VGA compatible controller product: 82945G/GZ Integrated Graphics Controller vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 version: 02 width: 32 bits clock: 33MHz capabilities: msi pm vga_controller bus_master cap_list rom configuration: driver=i915 latency=0 resources: irq:16 memory:dfe00000-dfe7ffff ioport:8800(size=8) memory:e0000000-efffffff memory:dfe80000-d$

  Read the article

• how to install ubuntu on imac

  - by leviathan

  i need help! im still new to this. i really need help, i have an imac.. (it's corrupted. when i try to open it, it shows a question mark alternating with a smiley) Model Family: iMac G5 Processor: 1.8GHz G5 (PowerPC 970fx) Manufacturer: Motorola of CPUs: 1 Size: 17" Finish: Matte Resolution: 1440x900 Backlight: CCFL Base Memory: 256MB PC3200 DIMM Max Memory: 2GB Memory Slots: 2 Brand: Apple Original OS: Mac OS X 10.3.5 i think it's vintage. haha. but i want to fix it. first, i think the hard drive is broken (pretty much corrupted) but i tried to install a xubuntu os on it because i don't have any other disc. but i think xubuntu is not compatible because i can't seem to get pass through the partitioning part. could some one please help..

  Read the article

• ubuntu 14.04 slow

  - by TURN A

  so i upgraded to ubuntu 14.04 from 12.04 with a usb but i have internet ,my computer is really slow at 1024x768 definition ,everything works super slow ,windows closing and opening and streaming videos ,everything ive used so far.but it works fine at 800x600 definition ,i want it to be fine at the higher definition ,how do i make it run well at 1024x768 ? in additional drivers nothing shows ,and my computer mirrors by default for some reason ,i tried stopping it from mirroring but most buttons dont want to work and weird glitches happen ,the system doesnt work well when not mirroring , i dont care if it mirrors or not i just want good performance .thank you in advance for any answers !! here are the computer specs Processor 1.8 GHz 8032 RAM 2 GB DDR3 Memory Speed 1066 MHz Hard Drive 32 GB Graphics Coprocessor Graphics Media Accelerator HD Wireless Type 802.11B, 802.11G, 802.11n Number of USB 2.0 Ports 4 Expand Other Technical Details Brand Name Asus Item model number EB1030-B003L Hardware Platform Linux Operating System Ubuntu Item Weight 1.5 pounds Item Dimensions L x W x H 1.14 x 6.70 x 8.60 inches Color Black Processor Brand Intel Processor Count 1 Computer Memory Type DDR3 SDRAM Flash Memory Size 32 Hard Drive Interface Solid State Optical Drive Type No

  Read the article

• Dual display setup - only one displayed after logon

  - by oneofthemany

  During boot process my desktop shows both Monitors, but after log I only get one. I'm using Ubuntu 11.10 When I go into Displays its still only shows on Monitor. Here is my graphics card details: 01:00.0 VGA compatible controller: nVidia Corporation G72 [GeForce 7300 LE] (rev a1) (prog-if 00 [VGA controller]) Subsystem: Dell Device 0405 Flags: bus master, fast devsel, latency 0, IRQ 16 Memory at dd000000 (32-bit, non-prefetchable) [size=16M] Memory at c0000000 (64-bit, prefetchable) [size=256M] Memory at de000000 (64-bit, non-prefetchable) [size=16M] [virtual] Expansion ROM at dfe00000 [disabled] [size=128K] Capabilities: <access denied> Kernel driver in use: nvidia Kernel modules: nvidia_96, nvidia_173, nouveau, nvidiafb

  Read the article

• Why would Copying a Large Image to the Clipboard Freeze a Computer?

  - by Akemi Iwaya

  Sometimes, something really odd happens when using our computers that makes no sense at all…such as copying a simple image to the clipboard and the computer freezing up because of it. An image is an image, right? Today’s SuperUser post has the answer to a puzzled reader’s dilemna. Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites. Original image courtesy of Wikimedia. The Question SuperUser reader Joban Dhillon wants to know why copying an image to the clipboard on his computer freezes it up: I was messing around with some height map images and found this one: (http://upload.wikimedia.org/wikipedia/commons/1/15/Srtm_ramp2.world.21600×10800.jpg) The image is 21,600*10,800 pixels in size. When I right click and select “Copy Image” in my browser (I am using Google Chrome), it slows down my computer until it freezes. After that I must restart. I am curious about why this happens. I presume it is the size of the image, although it is only about 6 MB when saved to my computer. I am also using Windows 8.1 Why would a simple image freeze Joban’s computer up after copying it to the clipboard? The Answer SuperUser contributor Mokubai has the answer for us: “Copy Image” is copying the raw image data, rather than the image file itself, to your clipboard. The raw image data will be 21,600 x 10,800 x 3 (24 bit image) = 699,840,000 bytes of data. That is approximately 700 MB of data your browser is trying to copy to the clipboard. JPEG compresses the raw data using a lossy algorithm and can get pretty good compression. Hence the compressed file is only 6 MB. The reason it makes your computer slow is that it is probably filling your memory up with at least the 700 MB of image data that your browser is using to show you the image, another 700 MB (along with whatever overhead the clipboard incurs) to store it on the clipboard, and a not insignificant amount of processing power to convert the image into a format that can be stored on the clipboard. Chances are that if you have less than 4 GB of physical RAM, then those copies of the image data are forcing your computer to page memory out to the swap file in an attempt to fulfil both memory demands at the same time. This will cause programs and disk access to be sluggish as they use the disk and try to use the data that may have just been paged out. In short: Do not use the clipboard for huge images unless you have a lot of memory and a bit of time to spare. Like pretty graphs? This is what happens when I load that image in Google Chrome, then copy it to the clipboard on my machine with 12 GB of RAM: It starts off at the lower point using 2.8 GB of RAM, loading the image punches it up to 3.6 GB (approximately the 700 MB), then copying it to the clipboard spikes way up there at 6.3 GB of RAM before settling back down at the 4.5-ish you would expect to see for a program and two copies of a rather large image. That is a whopping 3.7 GB of image data being worked on at the peak, which is probably the initial image, a reserved quantity for the clipboard, and perhaps a couple of conversion buffers. That is enough to bring any machine with less than 8 GB of RAM to its knees. Strangely, doing the same thing in Firefox just copies the image file rather than the image data (without the scary memory surge). Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

  Read the article

• Slow draw on some apps and dynamic clocks not working properly with ATI/AMD proprietary drivers

  - by Rakeka

  I've recently purchased a new computer (around July 2010) and I've been having some problems with proprietary video drivers on Linux. The hardware is: Video: ATI/AMD Radeon HD 5870 (XFX HD-587X-ZNFC); Motherboard: Asus P7P55D-E Deluxe; Processor: Intel i5 750; Memory: Kingston Hyperx KHX1600C8D3K2/4GX (2x - 8GB Total); Power Supply: XFX P1-750B-CAG9; There are no overclocks, not even the memories (they are at 1333mhz due processor memory controller limitation). The operational system is a homebrew Linux distribution with the following software: Architecture: x86_64 (multilib) Kernel: 2.6.35.10 Xorg: 7.5 Window Manager: wmii-3.9.2 Video Driver: ATI/AMD Catalyst 10.12 There are no desktop effects programs like compiz fusion or beryl. The problems: With ATI/AMD proprietary driver, some applications are with slow draw/redraw, and, the same applications make the driver to increase the card clocks to maximum (0% gpu activity, only the clocks are increased). I dunno exactly how to describe the slow draw but I'll list some applications and symptoms. xterm Flickers a lot when drawing continuous output; When I'm in a workspace with fullscreen xterm, The gpu load stays at 12% in idle, and, with smaller xterm, smaller GPU load. "aticonfig --odgc" output: Default Adapter - ATI Radeon HD 5800 Series Core (MHz) Memory (MHz) Current Clocks : 157 300 Current Peak : 850 1200 Configurable Peak Range : [600-900] [900-1300] GPU load : 12% "aticonfig --pplib-cmd 'get activity'" output: Current Activity is Core Clock: 157MHZ Memory Clock: 300MHZ VDDC: 950 Activity: 12 percent Performance Level: 0 Bus Speed: 5000 Bus Lanes: 16 Maximum Bus Lanes: 16 More examples: mplayer time info flickers on terminal; "find /" flickers a lot (It takes some time to stop with control-c. But, If I change the workspace or put some window upon it, just after the control-c, it stops instantly); "cat somefile" if the file is big (Xorg.0.log for example) it takes some time to display; vim and less (ex: find / | less) don't have much problems, just a little flicker when scrolling; mplayer (no gui) Slow reproduction and seek with -vo x11; Tearing with -vo xv; Time info flickers on terminal (xterm consequence); gvim A little slow draw when scrolling with page up/page down; Firefox Slow draw/redraw on some pages like www.boadica.com.br and sometimes on www.youtube.com with flash enable (never noticed on many pages); Corruptions when informative yellow boxes are showing and scroll the page (an gray box appears at the same place of the informative box); "Wallpaper" After minimizing a fullscreen window or changing to an empty workspace it takes some time to redraw wallpaper. "Video Card" The core and memory clocks are increased with the events described above and on other situations like change workspace (even without wallpaper), minimize, maximize or move a window; Idle clocks: Core: 157mhz, Memory: 300mhz Full clocks: Core: 850mhz, Memory: 1200mhz xpdf Painful slow scrolling; display (from ImageMagick) Slow menus and sometimes slow image redraw; Programs that I use and are apparently without problems: gimp; pidgin; mplayer (-vo gl, gl2); blender; unigine heaven (better fps than on Windows); doom3; tibia; penumbra overture; amnesia the dark descent (wine); diablo 2 (wine); No problems on Windows (Windows 7 Ultimate 64bit). And special note to this: Full desktop effects from Debian and Ubuntu gnome appearance cpanel don't cause ANY problems, even the core and memory clocks don't increase when change workspace, minimize, maximize or move a window. What I've tested: Unsuccessful tests: Tested all drivers versions since 10.6 (released approximately when I've installed the first slackware in this PC); Tested other video card - ATI/AMD Radeon HD 5570 (XFX HD-557X-ZHF2); Tested some options on xorg.conf and that I've found googling (some of these options are commented on my xorg.conf. I'll send the links at the end of post); Tested some patches like 107_fedora_dont_fill_bg_none.patch and xserver-xorg-backclear.patch from Arch Linux Catalyst page (https://wiki.archlinux.org/index.php/ATI_Catalyst); Tested other distros and software versions: Tested XORG-7.6 on my own distribution; Tested Debian Squeeze (testing - from 2010-12-20); Tested Ubuntu Marverick (10.10); Tested Slackware 13.1; Distros info: Architecture: i386 Debian and Ubuntu with all default software (kernel, gnome, xorg, drivers); Slackware with Catalyst from AMD page and default window managers like: fvwm, xfce, and my own build of wmii; Successful tests: Tested other video card (only on my homebrew distro) - NVIDIA Geforce 7300GS with driver 260.19.29; That didn't shown the slow draw problems, but that card is a bit obsolete, so, dunno if that lacks features like the dynamic clocks. I don't dispose of other video cards like nvidia g/gt/gts/gtx 200~400~500 or Radeon HD 3000/4000/6000 to make more tests. Tested other hardware: Video: ATI/AMD Radeon HD 5570 (XFX HD-557X-ZHF2); Motherboard: Intel DG31PR; Processor: Core 2 Duo E6750; Software for that hardware: Fresh install of same distros (except for the mine) with same program versions; That video card (HD 5570) were full time at the maximum clocks (something like 500/750, don't remember) in all the operational systems (Windows XP and Windows 7 too), but it didn't shown the same problems that I have here. I've googled a lot about common problems with ATI/AMD proprietary drivers for Linux and didn't find similar problems, except by the Firefox corruptions, that the solutions were to disable ATI Direct2DAccel and use XAA. With XAA the problems persists and the other applications like pidgin and rest of Firefox showed the same problems of slow draw/redraw. Open source Drivers: With open source drivers (xf86-video-ati-6.13.2) I hadn't the same slow draw problems, but, had other problems, that, for now, make it no viable solution. I'll not discuss it here because this is another line of problems and will confuse everything. If it happens to be the only solution, I'll make another thread to discuss it. Logs and Configs: kernel .config dmesg xorg package list xorg.conf Xorg.0.log

  Read the article

• Best Practices - Core allocation

  - by jsavit

  This post is one of a series of "best practices" notes for Oracle VM Server for SPARC (also called Logical Domains) Introduction SPARC T-series servers currently have up to 4 CPU sockets, each of which has up to 8 or (on SPARC T3) 16 CPU cores, while each CPU core has 8 threads, for a maximum of 512 dispatchable CPUs. The defining feature of Oracle VM Server for SPARC is that each domain is assigned CPU threads or cores for its exclusive use. This avoids the overhead of software-based time-slicing and emulation (or binary rewriting) of system state-changing privileged instructions used in traditional hypervisors. To create a domain, administrators specify either the number of CPU threads or cores that the domain will own, as well as its memory and I/O resources. When CPU resources are assigned at the individual thread level, the logical domains constraint manager attempts to assign threads from the same cores to a domain, and avoid "split core" situations where the same CPU core is used by multiple domains. Sometimes this is unavoidable, especially when domains are allocated and deallocated CPUs in small increments. Why split cores can matter Split core allocations can silenty reduce performance because multiple domains with different address spaces and memory contents are sharing the core's Level 1 cache (L1$). This is called false cache sharing since even identical memory addresses from different domains must point to different locations in RAM. The effect of this is increased contention for the cache, and higher memory latency for each domain using that core. The degree of performance impact can be widely variable. For applications with very small memory working sets, and with I/O bound or low-CPU utilization workloads, it may not matter at all: all machines wait for work at the same speed. If the domains have substantial workloads, or are critical to performance then this can have an important impact: This blog entry was inspired by a customer issue in which one CPU core was split among 3 domains, one of which was the control and service domain. The reported problem was increased I/O latency in guest domains, but the root cause might be higher latency servicing the I/O requests due to the control domain being slowed down. What to do about it Split core situations are easily avoided. In most cases the logical domain constraint manager will avoid it without any administrative action, but it can be entirely prevented by doing one of the several actions: Assign virtual CPUs in multiples of 8 - the number of threads per core. For example: ldm set-vcpu 8 mydomain or ldm add-vcpu 24 mydomain. Each domain will then be allocated on a core boundary. Use the whole core constraint when assigning CPU resources. This allocates CPUs in increments of entire cores instead of virtual CPU threads. The equivalent of the above commands would be ldm set-core 1 mydomain or ldm add-core 3 mydomain. Older syntax does the same thing by adding the -c flag to the add-vcpu, rm-vcpu and set-vcpu commands, but the new syntax is recommended. When whole core allocation is used an attempt to add cores to a domain fails if there aren't enough completely empty cores to satisfy the request. See https://blogs.oracle.com/sharakan/entry/oracle_vm_server_for_sparc4 for an excellent article on this topic by Eric Sharakan. Don't obsess: - if the workloads have minimal CPU requirements and don't need anywhere near a full CPU core, then don't worry about it. If you have low utilization workloads being consolidated from older machines onto a current T-series, then there's no need to worry about this or to assign an entire core to domains that will never use that much capacity. In any case, make sure the most important domains have their own CPU cores, in particular the control domain and any I/O or service domain, and of course any important guests. Summary Split core CPU allocation to domains can potentially have an impact on performance, but the logical domains manager tends to prevent this situation, and it can be completely and simply avoided by allocating virtual CPUs on core boundaries.

  Read the article

• Organization &amp; Architecture UNISA Studies &ndash; Chap 6

  - by MarkPearl

  Learning Outcomes Discuss the physical characteristics of magnetic disks Describe how data is organized and accessed on a magnetic disk Discuss the parameters that play a role in the performance of magnetic disks Describe different optical memory devices Magnetic Disk The way data is stored on and retried from magnetic disks Data is recorded on and later retrieved form the disk via a conducting coil named the head (in many systems there are two heads) The writ mechanism exploits the fact that electricity flowing through a coil produces a magnetic field. Electric pulses are sent to the write head, and the resulting magnetic patterns are recorded on the surface below with different patterns for positive and negative currents The physical characteristics of a magnetic disk   Summarize from book   The factors that play a role in the performance of a disk Seek time – the time it takes to position the head at the track Rotational delay / latency – the time it takes for the beginning of the sector to reach the head Access time – the sum of the seek time and rotational delay Transfer time – the time it takes to transfer data RAID The rate of improvement in secondary storage performance has been considerably less than the rate for processors and main memory. Thus secondary storage has become a bit of a bottleneck. RAID works on the concept that if one disk can be pushed so far, additional gains in performance are to be had by using multiple parallel components. Points to note about RAID… RAID is a set of physical disk drives viewed by the operating system as a single logical drive Data is distributed across the physical drives of an array in a scheme known as striping Redundant disk capacity is used to store parity information, which guarantees data recoverability in case of a disk failure (not supported by RAID 0 or RAID 1) Interesting to note that the increase in the number of drives, increases the probability of failure. To compensate for this decreased reliability RAID makes use of stored parity information that enables the recovery of data lost due to a disk failure.   The RAID scheme consists of 7 levels…   Category Level Description Disks Required Data Availability Large I/O Data Transfer Capacity Small I/O Request Rate Striping 0 Non Redundant N Lower than single disk Very high Very high for both read and write Mirroring 1 Mirrored 2N Higher than RAID 2 – 5 but lower than RAID 6 Higher than single disk Up to twice that of a signle disk for read Parallel Access 2 Redundant via Hamming Code N + m Much higher than single disk Highest of all listed alternatives Approximately twice that of a single disk Parallel Access 3 Bit interleaved parity N + 1 Much higher than single disk Highest of all listed alternatives Approximately twice that of a single disk Independent Access 4 Block interleaved parity N + 1 Much higher than single disk Similar to RAID 0 for read, significantly lower than single disk for write Similar to RAID 0 for read, significantly lower than single disk for write Independent Access 5 Block interleaved parity N + 1 Much higher than single disk Similar to RAID 0 for read, lower than single disk for write Similar to RAID 0 for read, generally  lower than single disk for write Independent Access 6 Block interleaved parity N + 2 Highest of all listed alternatives Similar to RAID 0 for read; lower than RAID 5 for write Similar to RAID 0 for read, significantly lower than RAID 5  for write   Read page 215 – 221 for detailed explanation on RAID levels Optical Memory There are a variety of optical-disk systems available. Read through the table on page 222 – 223 Some of the devices include… CD CD-ROM CD-R CD-RW DVD DVD-R DVD-RW Blue-Ray DVD Magnetic Tape Most modern systems use serial recording – data is lade out as a sequence of bits along each track. The typical recording used in serial is referred to as serpentine recording. In this technique when data is being recorded, the first set of bits is recorded along the whole length of the tape. When the end of the tape is reached the heads are repostioned to record a new track, and the tape is again recorded on its whole length, this time in the opposite direction. That process continued back and forth until the tape is full. To increase speed, the read-write head is capable of reading and writing a number of adjacent tracks simultaneously. Data is still recorded serially along individual tracks, but blocks in sequence are stored on adjacent tracks as suggested. A tape drive is a sequential access device. Magnetic tape was the first kind of secondary memory. It is still widely used as the lowest-cost, slowest speed member of the memory hierarchy.

  Read the article

• Mastering snow and Java development at jDays in Gothenburg

  - by JavaCecilia

  Last weekend, I took the train from Stockholm to Gothenburg to attend and present at the new Java developer conference jDays. It was professionally arranged in the Swedish exhibition hall close to the amusement park Liseberg and we got a great deal out of the top-level presenters and hallway discussions. Understanding and Improving Your Java Process Our main purpose was to spread information on JVM and our monitoring tools for Java processes, so I held a crash course in the most important terms and concepts if you want to affect the performance of your Java process. From the beginning - the JVM specification to interpretation of heap usage graphs. For correct analysis, you also need to understand something about process memory - you need space for the Java heap (-Xms for initial size and -Xmx for max heap size), but the process memory also contain the thread stacks (to a size of -Xss), JVM internal data structures used for keeping track of Java objects on the heap, method compilation/optimization, native libraries, etc. If you get long pause times, make sure to monitor your application, see the allocation rate and frequency of pause times.My colleague Klara Ward then held a presentation on the Java Mission Control product, the profiling and diagnostics tools suite for HotSpot, coming soon. The room was packed and very appreciated, Klara demonstrated four different scenarios, e.g. how to diagnose and fix latencies due to lock contention for logging.My German colleague, OpenJDK ambassador Dalibor Topic travelled to Sweden to do the second keynote on "Make the Future Java". He let us in on the coming features and roadmaps of Java, now delivering major versions on a two-year schedule (Java 7 2011, Java 8 2013, etc). Also letting us in on where to download early versions of 8, to report problems early on. Software Development in teams Being a scout leader, I'm drilled in different team building and workshop techniques, creating strong groups - of course, I had to attend Henrik Berglund's session on building successful teams. He spoke about the importance of clear goals, autonomy and agreed processes. Thomas Sundberg ended the conference by doing live remote pair programming with Alex in Rumania and a concrete tips for people wanting to try it out (for local collaboration, remember to wash and change clothes). Memory Master Keynote The conference keynote was delivered by the Swedish memory master Mattias Ribbing, showing off by remembering the order of a deck of cards he'd seen once. He made it interactive by forcing the audience to learn a memory mastering technique of remembering ten ordered things by heart, asking us to shout out the order backwards and we made it! I desperately need this - bought the book, will get back on the subject. Continuous Delivery The most impressive presenter was Axel Fontaine on Continuous Delivery. Very well prepared slides with key images of his message and moved about the stage like a rock star. The topic is of course highly interesting, how to create an infrastructure enabling immediate feedback to developers and ability to release your product several times per day. Tomek Kaczanowski delivered a funny and useful presentation on good and bad tests, providing comic relief with poorly written tests and the useful rules of thumb how to rewrite them. To conclude, we had a great time and hope to see you at jDays next year :)

  Read the article

• trying to setup wireless

  - by JohnMerlino

  I'm trying to set up wireless on vostro 1520 dell laptop, with latest Ubuntu install. Here's the output of some of the commands that I was told to run: lshw -C network viggy@ubuntu:~$ lshw -C network WARNING: you should run this program as super-user. *-network description: Ethernet interface product: RTL8111/8168B PCI Express Gigabit Ethernet controller vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: pci@0000:08:00.0 logical name: eth0 version: 03 serial: 00:24:e8:da:84:25 size: 100Mbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: bus_master cap_list rom ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl_nic/rtl8168d-1.fw ip=192.168.2.6 latency=0 multicast=yes port=MII speed=100Mbit/s resources: irq:47 ioport:3000(size=256) memory:f6004000-f6004fff memory:f6000000-f6003fff memory:f6020000-f603ffff *-network description: Network controller product: BCM4312 802.11b/g LP-PHY vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:0e:00.0 version: 01 width: 64 bits clock: 33MHz capabilities: bus_master cap_list configuration: driver=b43-pci-bridge latency=0 resources: irq:18 memory:fa000000-fa003fff *-network DISABLED description: Wireless interface physical id: 1 logical name: wlan0 serial: 0c:60:76:05:ee:74 capabilities: ethernet physical wireless configuration: broadcast=yes driver=b43 driverversion=3.2.0-29-generic firmware=N/A multicast=yes wireless=IEEE 802.11bg lspci 00:00.0 Host bridge: Intel Corporation Mobile 4 Series Chipset Memory Controller Hub (rev 07) 00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07) 00:02.1 Display controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07) 00:1a.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 03) 00:1a.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 03) 00:1a.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 (rev 03) 00:1a.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 03) 00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03) 00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 (rev 03) 00:1c.1 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 2 (rev 03) 00:1c.2 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 3 (rev 03) 00:1c.3 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 4 (rev 03) 00:1c.4 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 5 (rev 03) 00:1c.5 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 6 (rev 03) 00:1d.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 03) 00:1d.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 03) 00:1d.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 (rev 03) 00:1d.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 03) 00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev 93) 00:1f.0 ISA bridge: Intel Corporation ICH9M LPC Interface Controller (rev 03) 00:1f.2 SATA controller: Intel Corporation 82801IBM/IEM (ICH9M/ICH9M-E) 4 port SATA Controller [AHCI mode] (rev 03) 00:1f.3 SMBus: Intel Corporation 82801I (ICH9 Family) SMBus Controller (rev 03) 08:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 03) 0e:00.0 Network controller: Broadcom Corporation BCM4312 802.11b/g LP-PHY (rev 01) 1a:00.0 FireWire (IEEE 1394): O2 Micro, Inc. Device 10f7 (rev 01) 1a:00.1 SD Host controller: O2 Micro, Inc. Device 8120 (rev 01) 1a:00.2 Mass storage controller: O2 Micro, Inc. Device 8130 (rev 01) iwconfig lo no wireless extensions. wlan0 IEEE 802.11bg ESSID:off/any Mode:Managed Access Point: Not-Associated Tx-Power=0 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:on eth0 no wireless extensions. At this point in time, I don't have wireless.

  Read the article

• Data breakpoints to find points where data gets broken

  - by raccoon_tim

  When working with a large code base, finding reasons for bizarre bugs can often be like finding a needle in a hay stack. Finding out why an object gets corrupted without no apparent reason can be quite daunting, especially when it seems to happen randomly and totally out of context. Scenario Take the following scenario as an example. You have defined the a class that contains an array of characters that is 256 characters long. You now implement a method for filling this buffer with a string passed as an argument. At this point you mistakenly expect the buffer to be 256 characters long. At some point you notice that you require another character buffer and you add that after the previous one in the class definition. You now figure that you don’t need the 256 characters that the first member can hold and you shorten that to 128 to conserve space. At this point you should start thinking that you also have to modify the method defined above to safeguard against buffer overflow. It so happens, however, that in this not so perfect world this does not cross your mind. Buffer overflow is one of the most frequent sources for errors in a piece of software and often one of the most difficult ones to detect, especially when data is read from an outside source. Many mass copy functions provided by the C run-time provide versions that have boundary checking (defined with the _s suffix) but they can not guard against hard coded buffer lengths that at some point get changed. Finding the bug Getting back to the scenario, you’re now wondering why does the second string get modified with data that makes no sense at all. Luckily, Visual Studio provides you with a tool to help you with finding just these kinds of errors. It’s called data breakpoints. To add a data breakpoint, you first run your application in debug mode or attach to it in the usual way, and then go to Debug, select New Breakpoint and New Data Breakpoint. In the popup that opens, you can type in the memory address and the amount of bytes you wish to monitor. You can also use an expression here, but it’s often difficult to come up with an expression for data in an object allocated on the heap when not in the context of a certain stack frame. There are a couple of things to note about data breakpoints, however. First of all, Visual Studio supports a maximum of four data breakpoints at any given time. Another important thing to notice is that some C run-time functions modify memory in kernel space which does not trigger the data breakpoint. For instance, calling ReadFile on a buffer that is monitored by a data breakpoint will not trigger the breakpoint. The application will now break at the address you specified it to. Often you might immediately spot the issue but the very least this feature can do is point you in the right direction in search for the real reason why the memory gets inadvertently modified. Conclusions Data breakpoints are a great feature, especially when doing a lot of low level operations where multiple locations modify the same data. With the exception of some special cases, like kernel memory modification, you can use it whenever you need to check when memory at a certain location gets changed on purpose or inadvertently.

  Read the article

• Concurrent Affairs

  - by Tony Davis

  I once wrote an editorial, multi-core mania, on the conundrum of ever-increasing numbers of processor cores, but without the concurrent programming techniques to get anywhere near exploiting their performance potential. I came to the.controversial.conclusion that, while the problem loomed for all procedural languages, it was not a big issue for the vast majority of programmers. Two years later, I still think most programmers don't concern themselves overly with this issue, but I do think that's a bigger problem than I originally implied. Firstly, is the performance boost from writing code that can fully exploit all available cores worth the cost of the additional programming complexity? Right now, with quad-core processors that, at best, can make our programs four times faster, the answer is still no for many applications. But what happens in a few years, as the number of cores grows to 100 or even 1000? At this point, it becomes very hard to ignore the potential gains from exploiting concurrency. Possibly, I was optimistic to assume that, by the time we have 100-core processors, and most applications really needed to exploit them, some technology would be around to allow us to do so with relative ease. The ideal solution would be one that allows programmers to forget about the problem, in much the same way that garbage collection removed the need to worry too much about memory allocation. From all I can find on the topic, though, there is only a remote likelihood that we'll ever have a compiler that takes a program written in a single-threaded style and "auto-magically" converts it into an efficient, correct, multi-threaded program. At the same time, it seems clear that what is currently the most common solution, multi-threaded programming with shared memory, is unsustainable. As soon as a piece of state can be changed by a different thread of execution, the potential number of execution paths through your program grows exponentially with the number of threads. If you have two threads, each executing n instructions, then there are 2^n possible "interleavings" of those instructions. Of course, many of those interleavings will have identical behavior, but several won't. Not only does this make understanding how a program works an order of magnitude harder, but it will also result in irreproducible, non-deterministic, bugs. And of course, the problem will be many times worse when you have a hundred or a thousand threads. So what is the answer? All of the possible alternatives require a change in the way we write programs and, currently, seem to be plagued by performance issues. Software transactional memory (STM) applies the ideas of database transactions, and optimistic concurrency control, to memory. However, working out how to break down your program into sufficiently small transactions, so as to avoid contention issues, isn't easy. Another approach is concurrency with actors, where instead of having threads share memory, each thread runs in complete isolation, and communicates with others by passing messages. It simplifies concurrent programs but still has performance issues, if the threads need to operate on the same large piece of data. There are doubtless other possible solutions that I haven't mentioned, and I would love to know to what extent you, as a developer, are considering the problem of multi-core concurrency, what solution you currently favor, and why. Cheers, Tony.

  Read the article

< Previous Page | 162 163 164 165 166 167 168 169 170 171 172 173  | Next Page >