| === Elimin8r is now known as Elimin8er | ||
| === lfaraone_ is now known as lfaraone | ||
| lesshaste | hi.. is there any way to enable an OOM killer on ubuntu? | 08:52 |
|---|---|---|
| lesshaste | It is very annoying to have to turn the PC off at the wall | 08:52 |
| hyperair | it's enabled by default afaik | 08:53 |
| lesshaste | hyperair, it really doesn't seem to be in practice | 08:53 |
| hyperair | you probably have too much swap | 08:54 |
| hyperair | it hangs, right? | 08:54 |
| lesshaste | hyperair, ah.. | 08:54 |
| hyperair | basically it needs time to fill up the swap, and thrash about for a bit | 08:54 |
| lesshaste | it is thrashing exactly | 08:54 |
| hyperair | only when it can't allocate more memory does it trigger OOM | 08:54 |
| hyperair | as long as there's more swap, it can allocate more memory | 08:54 |
| hyperair | and thrash some more | 08:54 |
| lesshaste | oh.. I want it to kill the process when it is thrashing which I see is a different problem | 08:54 |
| hyperair | yeah that's a different problem | 08:54 |
| lesshaste | because the thrashing is unkillable in effect | 08:54 |
| hyperair | i think you can play with overcommit ratio or something | 08:54 |
| hyperair | well | 08:55 |
| lesshaste | as I can't even get to a terminal to type "kill" | 08:55 |
| hyperair | depending on the size of your swap, you can actually just wait it out | 08:55 |
| hyperair | i've let a thrashing machine sit for 30 minutes, and it fixed itself | 08:55 |
| lesshaste | hyperair, I think that's potentially forever | 08:55 |
| hyperair | most of the time i don't have the patience and cut the power though | 08:55 |
| hyperair | or start hammering the sysrq keys | 08:55 |
| hyperair | ah | 08:55 |
| lesshaste | hyperair, if I have a process which takes 1 hour normally and starts thrashing | 08:55 |
| hyperair | AH | 08:55 |
| hyperair | yes | 08:55 |
| lesshaste | I could be waiting for years | 08:55 |
| hyperair | there's a sysrq key that triggers the OOM killer | 08:55 |
| lesshaste | oh! | 08:55 |
| hyperair | https://en.wikipedia.org/wiki/Magic_SysRq_key | 08:56 |
| hyperair | alt+sysrq+f | 08:56 |
| hyperair | you need to enable it though | 08:56 |
| lesshaste | interesting | 08:56 |
| hyperair | see /etc/sysctl.d/10-magic-sysrq.conf | 08:56 |
| lesshaste | how do you get sysrq? It is in small letters on the prt sc key | 08:56 |
| hyperair | yeah | 08:56 |
| lesshaste | oh I need to enable it | 08:57 |
| hyperair | start by trying to get hitting alt+sysrq+h. i think that dumps a help message into dmesg | 08:57 |
| lesshaste | it tried to take a screenshot :) | 08:57 |
| lesshaste | let me try alt+shift | 08:57 |
| hyperair | lol | 08:57 |
| hyperair | i actually use the prtsc key | 08:57 |
| hyperair | alt+prtsc+whatever | 08:57 |
| hyperair | i disabled the screenshot taking though | 08:58 |
| lesshaste | it just tries to take a screenshot | 08:58 |
| hyperair | you may or may not need the fn key on a laptop | 08:58 |
| lesshaste | it's a desktop | 08:59 |
| hyperair | right | 08:59 |
| lesshaste | [ 823.370296] SysRq : This sysrq operation is disabled. | 08:59 |
| hyperair | hah | 08:59 |
| lesshaste | so that's something :) | 08:59 |
| hyperair | that's something, yes | 08:59 |
| hyperair | see the file i mentioned | 09:00 |
| hyperair | it's disabled by default because an attacker trying his/her luck might get lucky and kill the screensaver process without killing X | 09:00 |
| lesshaste | it says kernel.sysrq = 176 | 09:01 |
| lesshaste | which should be allow reboot/poweroff, enable remount read-only, enable sync command | 09:01 |
| lesshaste | how do you enable it if not in that file? | 09:01 |
| hyperair | sysctl kernel.sysrq=whatever | 09:02 |
| hyperair | as root | 09:02 |
| lesshaste | hyperair, so what role that does file play? | 09:02 |
| lesshaste | does that | 09:02 |
| hyperair | default sysctl setting | 09:02 |
| lesshaste | I mean /etc/sysctl.d/10-magic-sysrq.conf | 09:03 |
| hyperair | for making it persistent across reboots | 09:03 |
| lesshaste | what I mean is.. why isn't it enabled given that it is currentluy 176 | 09:03 |
| hyperair | sysctl changes kernel parameters. that usually lasts until you reboot | 09:03 |
| hyperair | oh | 09:03 |
| hyperair | well | 09:03 |
| hyperair | i dunno | 09:03 |
| hyperair | what does "sysctl kernel.sysrq" say? | 09:03 |
| lesshaste | I should say I have an unmodified ubuntu install | 09:03 |
| lesshaste | sysctl kernel.sysrq | 09:04 |
| lesshaste | kernel.sysrq = 176 | 09:04 |
| hyperair | i think it just allows a certain number of functions | 09:04 |
| lesshaste | oh i see | 09:04 |
| hyperair | here's mine: [3277566.690317] sysrq: SysRq : HELP : loglevel(0-9) reboot(b) crash(c) terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i) thaw-filesystems(j) sak(k) show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n) poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s) show-task-states(t) unmount(u) force-fb(V) show-blocked-tasks(w) dump-ftrace-buffe | 09:04 |
| hyperair | r(z) | 09:04 |
| lesshaste | what do you get from sysctl kernel.sysrq ? | 09:04 |
| hyperair | 1 | 09:05 |
| lesshaste | ok done | 09:05 |
| lesshaste | I really need a way to do alt-sys rq+h without it taking a screenshot! | 09:07 |
| lesshaste | aha! | 09:08 |
| lesshaste | alg gr+prt sc+h does it | 09:08 |
| lesshaste | alt gr I mean | 09:08 |
| lesshaste | [ 1540.531549] SysRq : HELP : loglevel(0-9) reboot(b) crash(c) terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i) thaw-filesystems(j) sak(k) show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n) poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s) show-task-states(t) unmount(u) force-fb(V) show-blocked-tasks(w) dump-ftrace-buffer(z) | 09:08 |
| lesshaste | success | 09:08 |
| lesshaste | so what one would kill the task that is thrashing? | 09:09 |
| lesshaste | which one | 09:09 |
| lesshaste | hyperair, thanks for you help | 09:18 |
| Eduard_Munteanu | Are the kernel Git repos hosted over https somewhere? | 12:48 |
| apw | Eduard_Munteanu, checking | 13:14 |
| apw | Eduard_Munteanu, yes, https:// is one of the options: https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/xenial | 13:15 |
| Eduard_Munteanu | apw, thanks | 13:18 |
| Eduard_Munteanu | Any reason kernel.ubuntu.org doesn't support it, btw? | 13:18 |
| * Eduard_Munteanu should file a bug perhaps | 13:18 | |
| apw | Eduard_Munteanu, likely because the machine was old and slow | 13:23 |
| apw | Eduard_Munteanu, the launchpad repos are going to become the official ones before long in all likelyhood | 13:23 |
| Eduard_Munteanu | Ah, nice. | 13:24 |
| apw | as that infrastructure is much more load tollerant | 13:24 |
| apw | Eduard_Munteanu, for xily and xenial LP is alreday master, and all others are sync'd up to LP every 15m or so | 13:31 |
| Eduard_Munteanu | Cool. | 13:32 |
| === alai888 is now known as alai | ||
| === caribou_ is now known as caribou | ||
| === dkessel_ is now known as dkessel | ||
| === jdstrand_ is now known as jdstrand | ||
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