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Showing posts from April, 2010

Show real swap usage for each individual process

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Update: the kernel patch is already in 2.6.34-rcN. Currently, in top, the SWAP column only shows the difference between VIRT and RES: case P_SWP: MKCOL(scale_num(PAGES_TO_KB(p->size - p->resident), w, s)); So currently the value is of no use. As a matter of fact, a recent enough kernel has provided the information which is needed to calculate the swap usage for each process. It is in /proc/$PID/smaps. But using smaps may affect top's performance because you have to calculate the sum yourself. But with this patch https://patchwork.kernel.org/patch/56929/ , the kernel will keep track of each process's swap usage for you. This patch (maybe not exactly in the same shape) is already in mmotm tree ( http://userweb.kernel.org/~akpm/mmotm/ ) 2.6.34-rcN. However, checking the /proc/$PID/status file directly may not be a thing which people would like to do. So I decided to make a patch for ps and top. Now it seems to be working. This is the vanilla ps: $ ps -o m_swap

Generate coredumps automatically in specified directory

If you are into investigating coredumps, or you are just curious about how many processes have coredumped, then this is for you: 1. add the following line to /etc/security/limits.conf * - core unlimited 2. add the following line to /etc/sysctl.conf kernel.core_pattern = /corefiles/core.%e.%p %e is the executable filename, %p is pid. Please check the "Naming of core dump files" section of man 5 core for more information on this. 3. run "sysctl -p", then logout and login. Or just reboot. This is what I have on my Yeeloong: $ ls /corefiles/ core.genstrings.11832 core.nscd.10278 core.nscd.12821 core.nscd.13617 core.nscd.23172 core.nscd.29367 core.nscd.6428 core.genstrings.18210 core.nscd.10281 core.nscd.13061 core.nscd.13620 core.nscd.23175 core.nscd.29368 core.nscd.6431 core.main.19478 core.nscd.10284 core.nscd.13064 core.nscd.19028 core.nscd.24042 core.nscd.29369 core.main.19702 core.