linux-kernel - Re: [RESEND PATCH V2] mm: page_alloc: unreserve highatomic page blocks before oom

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Message-ID: <Za-h5t7HX5rNrVdq@tiehlicka>
Date: Tue, 23 Jan 2024 12:24:22 +0100
From: Michal Hocko <mhocko@...e.com>
To: Joakim Tjernlund <Joakim.Tjernlund@...inera.com>
Cc: "david@...hat.com" <david@...hat.com>,
	"quic_pkondeti@...cinc.com" <quic_pkondeti@...cinc.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"hannes@...xchg.org" <hannes@...xchg.org>,
	"mgorman@...hsingularity.net" <mgorman@...hsingularity.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"vbabka@...e.cz" <vbabka@...e.cz>,
	"quic_charante@...cinc.com" <quic_charante@...cinc.com>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	"quic_cgoldswo@...cinc.com" <quic_cgoldswo@...cinc.com>
Subject: Re: [RESEND PATCH V2] mm: page_alloc: unreserve highatomic page
 blocks before oom

On Tue 23-01-24 11:08:28, Joakim Tjernlund wrote:
[...]
> Mar  9 12:52:40 xr kern.warn kernel: [ 1066.001379] Mem-Info:
> Mar  9 12:52:40 xr kern.warn kernel: [ 1066.003665] active_anon:18 inactive_anon:2435 isolated_anon:0
> Mar  9 12:52:40 xr kern.warn kernel: [ 1066.003665]  active_file:1 inactive_file:0 isolated_file:0
> Mar  9 12:52:40 xr kern.warn kernel: [ 1066.003665]  unevictable:267 dirty:0 writeback:0
> Mar  9 12:52:40 xr kern.warn kernel: [ 1066.003665]  slab_reclaimable:384 slab_unreclaimable:2223
> Mar  9 12:52:40 xr kern.warn kernel: [ 1066.003665]  mapped:1 shmem:0 pagetables:309 bounce:0
> Mar  9 12:52:41 xr kern.warn kernel: [ 1066.003665]  kernel_misc_reclaimable:0
> Mar  9 12:52:41 xr kern.warn kernel: [ 1066.003665]  free:1054 free_pcp:24 free_cma:0
> Mar  9 12:52:41 xr kern.warn kernel: [ 1066.037938] Node 0 active_anon:72kB inactive_anon:9740kB active_file:4kB inactive_file:0kB unevictable:1068kB isolated(anon):0kB isolated(file):0kB mapped:4kB dirty:0kB writeback:0kB shmem:0kB writeback_tmp:0kB kernel_stack:9
> Mar  9 12:52:41 xr kern.warn kernel: [ 1066.061723] Normal free:4216kB min:128kB low:160kB high:192kB reserved_highatomic:4096KB active_anon:72kB inactive_anon:9740kB active_file:4kB inactive_file:0kB unevictable:1068kB writepending:0kB present:36864kB managed:2944
> Mar  9 12:52:41 xr kern.warn kernel: [ 1066.087595] lowmem_reserve[]: 0 0
> Mar  9 12:52:41 xr kern.warn kernel: [ 1066.090918] Normal: 206*4kB (MEH) 198*8kB (UMEH) 79*16kB (UMEH) 13*32kB (H) 2*64kB (H) 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 4216kB
> Mar  9 12:52:41 xr kern.warn kernel: [ 1066.104104] 269 total pagecache pages
> Mar  9 12:52:41 xr kern.warn kernel: [ 1066.107768] 9216 pages RAM

OK, so this is really a tiny system (36MB) and having 4MB in highatomic
reserves is clearly too much. So this matches the patch you are
referencing and it migh help you indeed.

Thanks!

-- 
Michal Hocko
SUSE Labs