I am a little concerned with the amount of resources that I can use in a shared machine. Is there any way to test if the administrator has a limit in the amount of resources that I can use? And if does, to make a more complete question, how can I set up such limit?
For process related limits, you can have a look in /etc/security/limits.conf (read the comments in the file, use google or use man limits.conf for more information). And as jpalecek points out, you may use ulimit -a to see (and possibly modify) all such limits currently in effect.
You can use the command quota to see if a disk quota is in effect.
You can try running
ulimit -a
to see what resource limits are in effect. Also, if you are allowed to change such limits, you can change them by the ulimit command, eg.
ulimit -c unlimited
lifts any limit for a size of a core file a process can make.
At the C level, the relevant functions (actually syscalls(2)...) could be setrlimit(2) and setpriority(2) and sched_setattr(2). You probably would want them to be called from your shell.
See also proc(5) -and try cat /proc/self/limits and sched(7).
You may want to use the renice(1) command.
If you run a long-lasting program (for several hours) not requiring user interaction, you could consider using some batch processing. Some Linux systems have a batch or at command.
Related
I have a C program on Ubuntu. This program needs to open a lot of files. So I have to run it as the following:
ulimit -n 10000; ./xyz
Wonder if there is a way to do something within the program xyz itself to increase the limit. The program runs as root user, so it has the necessary privilege. In the C program (source code), I called
system("ulimit -n 10000");
But it doesn't work, which is not surprise.
See getrlimit(2)
Consider using the getrlimit(2) and setrlimit(2) routines. Note that only a process running with superuser privilege can increase a limit; any user can reduce their resource limits.
why not write a wrapper?
xyz_wrapper.sh
ulimit -n 10000; ./xyz
then simply run the wrapper
./xyz_wrapper.sh
I'm new to Linux and Terminal (or whatever kind of command prompt it uses), and I want to control the amount of RAM a process can use. I already looked for hours to find an easy-t-use guide. I have a few requirements for limiting it:
Multiple instances of the program will be running, but I only want to limit some of the instances.
I do not want the process to crash once it exceeds the limit. I want it to use HDD page swap.
The program will run under WINE, and is a .exe.
So can somebody please help with the command to limit the RAM usage on a process in Linux?
The fact that you’re using Wine makes no difference in this particular context, which leaves requirements 1 and 2. Requirement 2 –
I do not want the process to crash once it exceeds the limit. I want it to use HDD page swap.
– is known as limiting the resident set size or rss of the process, and it’s actually rather nontrivial to do on Linux, as is demonstrated by a question asked in 2010. You’ll need to set up Linux control groups (cgroups). Fortunately, Justin L.’s answer gives a brief rundown on how to do so. Note that
instead of jlebar, you should use your own Unix user name, and
instead of your/program, you should use wine /path/to/Windows/program.exe.
Using cgroups will also satisfy your other requirements – you can start as many instances of the program as you wish, but only those which you start with cgexec -g memory:limited will be limited.
I would like to limit memory used by a process started through bash with the ulimit command on Linux. I was wondering what OS mechanism is used to support ulimit. In particular, is it based on cgroups?
The Linux API methods for getting and setting limits are getrlimit(2) and setrlimit(2)
Limits are managed within the process space. A child process will inherit the limits of its parent. Limits are part of the POSIX standard, so all POSIX compliant operating systems support them (Linux, BSD, OSX).
cgroups are Linux specific, and are not even required in a Linux install. I'm not sure if it is possible to manage limits with cgroups, but it would definitely be non-standard do to so.
"ulimit" is basically an anachronism. You shouldn't have any real limits out of the box if you need the resources, and there are better ways to establish quotes if you want to limit resources.
Here's a good overview:
http://www.gnu.org/software/libc/manual/html_node/Limits-on-Resources.html
Several man pages to look at include:
man 2 getrlimit
man 2 setrlimit
man 3 ulimit OBSOLETE!
I use softlimit, part of DJB's daemontools package.
By specifying something like softlimit -m 1048576 nautilus for example, the program (nautilus) will never exceed 1MiB of memory usage (which also causes it to fail immediately in this case).
I am totally confused by obtaining the limits of open file descriptors in Linux.
which value is correct by them?
ulimit -n ======> 65535
but
vim /etc/security/limits.conf
soft nofile 50000
hard nofile 90000
The limits applied in /etc/security/limits.conf are applied by the limits authentication module at login if it's part of the PAM configuration. Then the shell gets invoked which can apply it's own limits to the shell.
If you're asking which one is in effect, then it's the result from the ulimit call. if it's not invoked with the -H option, then it displays the soft limit.
The idea behind the limits.conf settings is to have a global place to apply limits for, for example, remote logins
Limits for things like file descriptors can be set at the user level, or on a system wide level. /etc/security/limits.conf is where you can set user level limits, which might be different limits for each user, or just defaults that apply to all users. The example you show has a soft (~warning) level limit of 50000, but a hard (absolute maximum) limit of 90000.
However, a system limit of 65535 might be in place, which would take precedence over the user limit. I think system limits are set in /etc/sysctl.conf, if my memory serves correctly. You might check there to see if you're being limited by the system.
Also, the ulimit command can take switches to specifically show the soft (-Sn) and hard (-Hn) limits for file descriptors.
i think this conf is used by all the apps in the system. if you do want to change one particular app, you can try setrlimit() or getrlimt(). man doc dose explain everything.
I want to use the /proc to find the resource usage of a particular process every second. The resources include cputime, disk usage and network usage. I looked at /proc/pid/stat , but I am not sure whether I am getting the required details. I want all 3 resource usage and I want to monitor them every second.
Some newer kernels have /proc/<pid_of_process>/io file. This is where IO stats are.
It is not documented in man proc, but you can try to figure out the numbers yourself.
Hope it helps.
Alex.
getrusage() accomplishes cpu, memory and disk etc.
man 2 getrusage
I don't know about network.
checkout glances.
It's got cpu disk and network all on one screen. It's not per process but it's better than looking at 3 separate tools.
Don't think there is a way to get the disk and network information on a per process basis.
The best you can have is the global disk and network, and the per process CPU time.
All documented in man proc
netstat -an
Shows all connections to the server including the source and destination ips and ports if you have proper permissions.
ac
Prints statistics about users' connect time
The best way to approach problems like this is to look up the source code of tools that perform similar monitoring and reporting.
Although there is no guarantee that they are using /proc directly, they will lead you to an efficient way to tackle the problem.
For your case, top(1), iotop(8) and nethogs(8) come to mind.
You can use SAR
-x report statistics for a given process.
See this for more details:
http://www.linuxcommand.org/man_pages/sar1.html
Example:
sar -u -r -b 1 -X PID | grep -v Average | grep -v Linux
You can use top
SYNOPSIS
top -hv|-bcHiOSs -d delay -n limit -u|U user -p PID -o champ -w [columns]
This is a screen capture of top in a terminal