On 2017/12/09 6:02, David Rientjes wrote:
> On Thu, 7 Dec 2017, Suren Baghdasaryan wrote:
>
>> Slab shrinkers can be quite time consuming and when signal
>> is pending they can delay handling of the signal. If fatal
>> signal is pending there is no point in shrinking that process
>> since it will be killed anyway. This change checks for pending
>> fatal signals inside shrink_slab loop and if one is detected
>> terminates this loop early.
>>
>
> I've proposed a similar patch in the past, but for a check on TIF_MEMDIE,
> which would today be a tsk_is_oom_victim(current), since we had observed
> lengthy stalls in reclaim that would have been prevented if the oom victim
> had exited out, returned back to the page allocator, allocated with
> ALLOC_NO_WATERMARKS, and proceeded to quickly exit.
>
> I'm not sure that all fatal_signal_pending() tasks should get the same
> treatment, but I understand the point that the task is killed and should
> free memory when it fully exits. How much memory is unknown.
>
We can use __GFP_KILLABLE. Unless there is performance impact for checking
fatal_siganl_pending(), allowing only fatal_signal_pending() threads with
__GFP_KILLABLE to bail out (without using memory reserves) should be safe.
