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  • aio_write on linux with rtkaio is sometimes long

    - by Drakosha
    I'm using async io on linux with rtkaio library. In my tests everything works perfectly, but, in my real application i see that aio_write which is supposed to return very fast, is very slow. It can take more than 100 milis to write a 128KB to a O_DIRECT padded file. Both my test and the application use same I/O size, i check on the same file system (GFS). I added counting and i see that there are about 50% of async io operations that are short (shorter then 2 milis) and 50% that are long (longer than 2 milis). I also checked that the test and the application both use the same rtkaio library. I'm pretty lost, anyone any ideas where should i look? Another my related question: http://stackoverflow.com/questions/1799537/proc-sys-fs-aio-nr-is-never-higher-than-1024-aio-on-linux

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  • linux display drivers

    - by salman
    I've run into a major display problem on newly installed fedora 11, on my 6 years old pc which runs a pentium4 2.4 GHz processor, 1 gb ddr ram, intel 845 motherboard with integrated graphics card. When i open an image or play a video, my complete screen turns garbled. I simply cannot make out whats on my screen. With difficulty i have to close the image/video window and move around the folder window to clean the screen image. Is it because of my display drivers? How can i fix it? I also ran into mp3 plugins and flash issues which i was able to resovle. I'm new to linux, the sole purpose of isntalling it on my old pc was to learn linux but this display problem is frustrating me. Thanks, Salman

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  • Linux - Create ftp account with read/write access to only 1 folder

    - by Gublooo
    Hey guys.... I have never worked on linux and dont plan on working on it either - The only command I probably know is "ls" :) I am hosting my website on Eapps and use their cpanel to setup everything so never worked with linux. Now I have this one time case - where I need to provide access to a contractor to fix the CSS issues on my website. He basically needs FTP (read/write) access to certain folders. At a high level - this is my code structure /home/webadmin/example.com/html/images /css /js /login.php /facebook.php /home/webadmin/example.com/application/library /views /models /controllers /config /bootstrap.php /home/webadmin/example.com/cgi-bin I want the new user to be able to have access to only these folders /home/webadmin/example.com/html/js /home/webadmin/example.com/html/css /home/webadmin/example.com/application/views He should not be able to view even the content of other folders including files like bootstrap.php or login.php etc If any sys admins can help me set this account up - will really appreciate it. Thanks

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  • When to best implement a I2C driver module in Linux

    - by stefangachter
    I am currently dealing with two devices connected to the I2C bus within an embedded system running Linux. I am using an exisiting driver for the first device, a camera. For the second device, I have successfully implemented a userspace program with which I can communicate with the second device. So far, both devices seem to coexist happily. However, almost all I2C devices have their own driver module. Thus, I am wondering what the advantages of a driver module are. I had a look at the following thread... http://stackoverflow.com/questions/149032/when-should-i-write-a-linux-kernel-module ... but without conclusion. Thus, what would be the advantage of writing a I2C driver module over a userspace implementation? Regards, Stefan

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  • Cross-compiling a Python script on Linux into a Windows executable

    - by Chinmay Kanchi
    I have a Python script that I'd like to compile into a Windows executable. Now, py2exe works fine from Windows, but I'd like to be able to run this from Linux. I do have Windows on my development machine, but Linux is my primary dev platform and I'm getting kind of sick of rebooting into Windows just to create the .exe. Any ideas? PS: I am aware that py2exe doesn't exactly compile the python file as much as package your script with the Python interpreter. But either way, the result is that you don't need Python installed to run the script.

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  • Linux / C++: Get the IP Address of local computer

    - by BlaM
    This Question is almost the same as the previously asked Get the IP Address of local computer-Question. However I need to find the IP address(es) of a Linux Machine. So: How do I - programmatically in C++ - detect the IP addresses of the linux server my application is running on. The servers will have at least two IP addresses and I need a specific one (the one in a given network (the public one)). I'm sure there is a simple function to do that - but where? [EDIT] To make things a bit clearer: The server will obviously have the "localhost": 127.0.0.1 The server will have an internal (management) IP address: 172.16.x.x The server will have an external (public) IP address: 80.190.x.x I need to find the external IP address to bind my application to it. Obviously I can also bind to INADDR_ANY (and actually that's what I do at the moment). I would prefer to detect the public address, though.

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  • Programming a loopback-device consisting of several files in Linux

    - by dubbaluga
    Hej, it is relatively easy to use a file for emulating a block-device using losetup in Linux: http://www.walkernews.net/2007/07/01/create-linux-loopback-file-system-on-disk-file/ Can anyone please give me a hint on what to look for in case I want to program my own block-device which is based on several files I'm taking content from? For your understanding, I would like to let's say take bytes 1-500 and 1.000-3.000 from file1 and bytes 501-999 and bytes 3.001 to 5.000 from file2 to offer them as a combined block-device. My prefered programming language is Python and I want to write my program in user-space as much as possible. For Windows I found such an implementation. It's called FileDisk and HttpDisk and it can be found here: http://www.acc.umu.se/~bosse/ Thanks in advance and regards, Rainer

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  • Best C++ Linux IDE [closed]

    - by Idan
    Possible Duplicate: Best unix/linux C++ debuger/IDE ? Hey, I've been searcing and reading about a good Linux C++ IDE, and couldn't set my mind on the right one. I've been using Eclipse with the C++ pluging , for C development, for the last couple months, but I found it not very useful, especially the debugging process that was quite annoying. I love Vistal Studio, so I'm looking for something really close to it. I need an IDE that will provide me, among other things: - rich debugging options - easy to use graphical designer - underscores error/warning (before I compile - like eclipse has) - Intellisense and more... Any suggestion? Maybe NetBeans?

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  • Faster forking of large processes on Linux ?

    - by timday
    What's the fastest, best way on modern Linux of achieving the same effect as a fork-execve combo from a large process ? My problem is that the process forking is ~500MByte big, and a simple benchmarking test achieves only about 50 forks/s from the process (c.f ~1600 forks/s from a minimally sized process) which is too slow for the intended application. Some googling turns up vfork as having being invented as the solution to this problem... but also warnings about not to use it. Modern Linux seems to have acquired related clone and posix_spawn calls; are these likely to help ? What's the modern replacement for vfork ? I'm using 64bit Debian Lenny on an i7 (the project could move to Squeeze if posix_spawn would help).

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  • Monitor file in Java on Linux 64bits

    - by Tim
    I'd like to be notified when a file has been created, deleted or changed, but not using polling mechanism. I have surveyed related Java API that can use.(EX:JNotify, JPathWatch and JXFileWatcher) Those APIs provide file monitor by using native component on OS. But I met the same problem is that they can't run on Linux 64bits, because native component in those APIs donen't support Linux 64bits, and this confused me for a long time. I also know that there'll be a WatchService API as part of NIO2 in JDK7, but JDK7 has not released yet. So, can any one suggest me a better solution? Very Thanks.

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  • How does Linux blocking I/O actually work?

    - by tgguy
    In Linux, when you make a blocking i/o call like read or accept, what actually happens? My thoughts: the process get taken out of the run queue, put into a waiting or blocking state on some wait queue. Then when a tcp connection is made (for accept) or the hard drive is ready or something for a file read, a hardware interrupt is raised which lets those processes waiting to wake up and run (in the case of a file read, how does linux know what processes to awaken, as there could be lots of processes waiting on different files?). Or perhaps instead of hardware interrupts, the individual process itself polls to check availability. Not sure, help?

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  • LBA48 in Linux SCSI ATA Passthrough

    - by Ben Englert
    I am writing a custom disk monitoring/diagnostics app which, among other things, needs to do stuff to SATA disks behind a SAS PCI card under Linux. So far I am following this guide as well as the example code in sg_utils to pass ATA taskfiles through the SCSI layer. Seems to be working okay. However, in both cases, the CDB data structure (pointed to by the cmdp member of the sg_io argument to the ioctl) has only one unsigned char worth of space for the number of sectors. If you look at the ata_taskfile structure in linux\ata.h you'll see that it has an "nsect" and a "hob_nsect" field - high order bits for the sector count, to support LBA48. It turns out that in my application I need LBA48 support. So, anyone know how to set up an sg_io_hdr structure with an LBA48 sector count?

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  • How to reliably measure available memory in Linux?

    - by Alex B
    Linux /proc/meminfo shows a number of memory usage statistics. MemTotal: 4040732 kB MemFree: 23160 kB Buffers: 163340 kB Cached: 3707080 kB SwapCached: 0 kB Active: 1129324 kB Inactive: 2762912 kB There is quite a bit of overlap between them. For example, as far as I understand, there can be active page cache (belongs to "cached" and "active") and inactive page cache ("inactive" + "cached"). What I want to do is to measure "free" memory, but in a way that it includes used pages that are likely to be dropped without a significant impact on overall system's performance. At first, I was inclined to use "free" + "inactive", but Linux's "free" utility uses "free" + "cached" in its "buffer-adjusted" display, so I am curious what a better approach is. When the kernel runs out of memory, what is the priority of pages to drop and what is the more appropriate metric to measure available memory?

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  • C++ Access to SQL Server from Linux

    - by Meloun
    I need to write some data to SQL Server database from Linux in c++. I found this sqlapi.com But I think, at first ODBC driver has to be installed an has to work. I folowed this adminlife.net/allgemein/mssql-zugriff-unter-debian-etch-mit-unixodbc-und-freetds/ or this http://b.gil.megiteam.pl/2009/11/linux-odbc-to-mssql/ But it didnt work, the port 1433 seems to be closed ($ sudo nmap -PN -sU -p 1433 192.168.56.101 - port "filtered") isql -v sqlexpress sa - wait with no response or get "couldn't connect to sql" From other PC with Windows I have no problem to write data in SQL Server, so server should be right configured to remote access. any idea?

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  • cset shield --kthread on: should I use this?

    - by lori
    I'm reading up on cpu shielding using Alex Tsariounov's cset utility here: https://rt.wiki.kernel.org/index.php/Cpuset_Management_Utility/tutorial In the tutorial I'm finding the wording around migrating kernel threads from having access to all cpus to running only in a certain cpuset a bit ambiguous The tutorial says the following: Some kernel threads can be moved into the unshielded system cpuset as well. These are the threads that are not bound to specific CPUs. If a kernel thread is bound to a specific CPU, then it is generally not a good idea to move that thread to the system set because at worst it may hang the system and at best it will slow the system down significantly. These threads are usually the IRQ threads on a real time Linux kernel, for example, and you may want to not move these kernel threads into system. If you leave them in the root cpuset, then they will have access to all CPUs. The tutorial then goes on to say: However, if your application demands an even "quieter" shield, then you can move all movable kernel threads into the unshielded system set with the following command. [zuul:cpuset-trunk]# cset shield -k on cset: --> activating kthread shielding cset: kthread shield activated, moving 70 tasks into system cpuset... [==================================================]% cset: done I am confused by this final sentence. By using the word however, it seems to suggest that you typically should not move the movable kernel threads into the unshielded system set. Is this the case, or is it safe to move kernel threads which can be moved into a cpuset, thereby preventing them from running on some cpus?

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  • Import C + Makefile into a linux IDE?

    - by Jessica
    I have a project for Linux that i've been developing for some time. Basically it's a bunch of C and H files together with a directory structure and a Makefile. Every time I need to debug something it's so painful, I need to manually search for var. definitions, structs, etc. Is there any good IDE out there for Linux that will allow me to import those files into a "project" and that will provide code completion or at least an easy way to get my bearings in the source code? thanks!

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  • C++ Access to MSSQL from Linux

    - by Meloun
    Hi, I need to write some data to mssql database from linux in c++. I found this sqlapi.com But I think, at first ODBC driver has to be installed an has to work. I folowed this adminlife.net/allgemein/mssql-zugriff-unter-debian-etch-mit-unixodbc-und-freetds/ or this http://b.gil.megiteam.pl/2009/11/linux-odbc-to-mssql/ But it didnt work, the port 1433 seems to be closed ($ sudo nmap -PN -sU -p 1433 192.168.56.101 - port "filtered") isql -v sqlexpress sa - wait with no response or get "coulndt connect to sql" From other PC with Windows I have no problem to write data in mssql, so server should be right configured to remote access. any idea?

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