linux-kernel - [PATCH V3 0/2] mm: page_alloc: fixes for high atomic reserve caluculations

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Date:   Fri, 24 Nov 2023 16:35:51 +0530
From:   Charan Teja Kalla <quic_charante@...cinc.com>
To:     <akpm@...ux-foundation.org>, <mgorman@...hsingularity.net>,
        <mhocko@...e.com>, <david@...hat.com>, <vbabka@...e.cz>,
        <hannes@...xchg.org>, <quic_pkondeti@...cinc.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Charan Teja Kalla <quic_charante@...cinc.com>
Subject: [PATCH V3 0/2] mm: page_alloc: fixes for high atomic reserve caluculations

The state of the system where the issue exposed shown in oom kill logs:
[  295.998653] Normal free:7728kB boost:0kB min:804kB low:1004kB
high:1204kB reserved_highatomic:8192KB active_anon:4kB inactive_anon:0kB
active_file:24kB inactive_file:24kB unevictable:1220kB writepending:0kB
present:70732kB managed:49224kB mlocked:0kB bounce:0kB free_pcp:688kB
local_pcp:492kB free_cma:0kB
[  295.998656] lowmem_reserve[]: 0 32
[  295.998659] Normal: 508*4kB (UMEH) 241*8kB (UMEH) 143*16kB (UMEH)
33*32kB (UH) 7*64kB (UH) 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB
0*4096kB = 7752kB

>From the above, it is seen that ~16MB of memory reserved for high atomic
reserves against the expectation of 1% reserves which is fixed in the
1st patch.

Don't reserve the high atomic page blocks if 1% of zone memory size is
below a pageblock size.

Changes in V3:
 o Seperated the patch of unreserving the high atomic pageblock done from
   should reclaim retry.
 o Don't reserve high atomic page blocks for smaller zone sizes.

Changes in V2:
 o Unreserving the high atomic page blocks is done from should_reclaim_retry()
 o Reserve minimum and max memory for high atomic reserves as a pageblock and
   1% of the memory zone respectively.
 o drain the pcp lists before falling back to OOM.
 o https://lore.kernel.org/linux-mm/cover.1699104759.git.quic_charante@quicinc.com/

Changes in V1:
 o Unreserving the high atomic page blocks is tried to fix from
   the oom kill path rather than in should_reclaim_retry()
 o discussed why a lot more than 1% of managed memory is reserved
   for high atomic reserves.
 o https://lore.kernel.org/linux-mm/1698669590-3193-1-git-send-email-quic_charante@quicinc.com/

Charan Teja Kalla (2):
  mm: page_alloc: correct high atomic reserve calculations
  mm: pagealloc: enforce minimum zone size to do high atomic reserves

 mm/page_alloc.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

-- 
2.7.4