Re: [PATCH 0/3] OOM detection rework v4

[Michal Hocko]

On Thu 25-02-16 17:17:45, Hillf Danton wrote:
[...]
> > OOM example:
> > 
> > [ 2392.663170] zram-test.sh invoked oom-killer: gfp_mask=0x27000c0(GFP_KERNEL_ACCOUNT|__GFP_NOTRACK), order=2,  oom_score_adj=0
[...]
> > [ 2392.663260] DMA: 4*4kB (M) 1*8kB (M) 4*16kB (ME) 1*32kB (M) 2*64kB (UE) 2*128kB (UE) 3*256kB (UME) 3*512kB (UME) 2*1024kB (ME) 1*2048kB (E) 2*4096kB (M) = 15096kB
> > [ 2392.663284] DMA32: 5809*4kB (UME) 3*8kB (M) 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 23260kB
> > [ 2392.663293] Normal: 1515*4kB (UME) 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 6060kB

[...]
> > [ 2400.152464] zram-test.sh invoked oom-killer: gfp_mask=0x27000c0(GFP_KERNEL_ACCOUNT|__GFP_NOTRACK), order=2, oom_score_adj=0
[...]
> > [ 2400.152558] DMA: 4*4kB (M) 1*8kB (M) 4*16kB (ME) 1*32kB (M) 2*64kB (UE) 2*128kB (UE) 3*256kB (UME) 3*512kB (UME)  2*1024kB (ME) 1*2048kB (E) 2*4096kB (M) = 15096kB
> > [ 2400.152573] DMA32: 7835*4kB (UME) 55*8kB (M) 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 31780kB
> > [ 2400.152582] Normal: 1383*4kB (UM) 22*8kB (UM) 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB =  5708kB
[...]
> Thanks for your info.
> 
> Can you please schedule a run for the diff attached, in which 
> non-expensive allocators are allowed to burn more CPU cycles.

I do not think your patch will help. As you can see, both OOMs were for
order-2 and there simply are no order-2+ free blocks usable for the
allocation request so the watermark check will fail for all eligible
zones and no_progress_loops is simply ignored. This is what I've tried
to address by patch I have just posted as a reply to Hugh's email
http://lkml.kernel.org/r/20160225092315.GD17573@xxxxxxxxxxxxxx

> --- a/mm/page_alloc.c	Thu Feb 25 15:43:18 2016
> +++ b/mm/page_alloc.c	Thu Feb 25 16:46:05 2016
> @@ -3113,6 +3113,8 @@ should_reclaim_retry(gfp_t gfp_mask, uns
>  	struct zone *zone;
>  	struct zoneref *z;
>  
> +	if (order <= PAGE_ALLOC_COSTLY_ORDER)
> +		no_progress_loops /= 2;
>  	/*
>  	 * Make sure we converge to OOM if we cannot make any progress
>  	 * several times in the row.
-- 
Michal Hocko
SUSE Labs