Re: Runaway process and oom-killer

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Chris Friesen wrote:

Helge Hafting wrote:

My guess:
Something needs memory but finds there is none to be had
oom-killer is invoked and targets myapp.
myapp takes some time to die. Particularly, the memory it uses
isn't freed up instantly.

Has anyone considered actually bumping up the priority of the task being killed so that it gets to run and free up its resources in a timely manner?

On this system,
myapp runs in SCHED_RR with priority 80.
IRQ handlers run in SCHED_FIFO with priority 50.

# ps -eo comm,class,rtprio,ni,pri --sort -rtprio
COMMAND         CLS RTPRIO  NI PRI
posix_cpu_timer FF      99   - 139
myapp           RR      80   - 120
softirq-high/0  FF      50   -  90
softirq-timer/0 FF      50   -  90
softirq-net-tx/ FF      50   -  90
softirq-net-rx/ FF      50   -  90
softirq-block/0 FF      50   -  90
softirq-tasklet FF      50   -  90
softirq-sched/0 FF      50   -  90
softirq-hrtimer FF      50   -  90
softirq-rcu/0   FF      50   -  90
IRQ-7           FF      50   -  90
IRQ-8           FF      50   -  90
IRQ-14          FF      50   -  90
IRQ-12          FF      50   -  90
IRQ-1           FF      50   -  90
IRQ-10          FF      50   -  90
IRQ-11          FF      50   -  90
IRQ-5           FF      50   -  90
IRQ-3           FF      50   -  90
IRQ-4           FF      50   -  90
events/0        FF       1   -  41
init            TS       -   0  24
desched/0       TS       - -10  34
khelper         TS       -  -5  29
kthread         TS       -  -5  27
kblockd/0       TS       -  -5  21
kacpid          TS       -  -5  19
kseriod         TS       -  -5  29
pdflush         TS       -   0  17
pdflush         TS       -   0  24
kswapd0         TS       -  -5  23
flush_filesd/0  TS       -  -5  29
aio/0           TS       -  -5  22
syslogd         TS       -   0  21
klogd           TS       -   0  21
sshd            TS       -   0  21
acpid           TS       -   0  16
agetty          TS       -   0  24
agetty          TS       -   0  21
agetty          TS       -   0  21
agetty          TS       -   0  21
[...]

How do the scheduling class and priority of the process come into play when the kernel comes to reclaim memory after the oom-killer has decided to snipe that particular process?

We've done some experimenting with actually putting it in SCHED_RR and it seems to help (in the case of other busy SCHED_RR tasks on the system). Admittedly we have an older kernel, so behaviour may be different now.

Thanks for sharing your experience.

Regards.
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