Re: [PATCH V3 3/3] mm: page_alloc: drain pcp lists before oom kill

[Michal Hocko]

On Tue 14-11-23 22:06:45, Charan Teja Kalla wrote:
> Thanks Michal!!
> 
> On 11/14/2023 4:18 PM, Michal Hocko wrote:
> >> At least in my particular stress test case it just delayed the OOM as i
> >> can see that at the time of OOM kill, there are no free pcp pages. My
> >> understanding of the OOM is that it should be the last resort and only
> >> after doing the enough reclaim retries. CMIW here.
> > Yes it is a last resort but it is a heuristic as well. So the real
> > questoin is whether this makes any practical difference outside of
> > artificial workloads. I do not see anything particularly worrying to
> > drain the pcp cache but it should be noted that this won't be 100%
> > either as racing freeing of memory will end up on pcp lists first.
> 
> Okay, I don't have any practical scenario where this helped me in
> avoiding the OOM.  Will comeback If I ever encounter this issue in
> practical scenario.
> 
> Also If you have any comments on [PATCH V2 2/3] mm: page_alloc: correct
> high atomic reserve calculations will help me.

I do not have a strong opinion on that one to be honest. I am not even
sure that reserving a full page block (4MB) on small systems as
presented is really a good use of memory.
-- 
Michal Hocko
SUSE Labs