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AJvYcCUGhuUr6dVwV0oSVdFElJWo/Ec2SnGfmC0HtMUhQqnS7Eq6E1DaGdWA7QVxQ1jeYuTRmbou8QufAA==@kvack.org X-Gm-Message-State: AOJu0YxHyWiYJsMISYKeehQ72q/OkKdtnkPKkS0TxfodOY1Kp5SB4mMw MbBx7fnLXMRE3+x08mgAMRn4GRZJS5tIodoNqwOKH2O4PKtkSQ0RZrjr+gtKccemfhip7C4hbdw ZrKc29eMSHMHntj0KwjPvO9BrNID8pSfI4KsH X-Google-Smtp-Source: AGHT+IHNn/80bAwbV/gVMgBG2OR6yzZFwt2z7VdJybvOFsuE/f7+OoV6aFj4QLToELhZAh1CaRLJsImbdT6goWg/5c4= X-Received: by 2002:a05:6102:3e82:b0:4a4:8b30:53e with SMTP id ada2fe7eead31-4a8cfb5de26mr3927354137.7.1730060290830; Sun, 27 Oct 2024 13:18:10 -0700 (PDT) MIME-Version: 1.0 References: <20241026033625.2237102-1-yuzhao@google.com> <37a28ef7-e477-40b0-a8e4-3d74b747e323@suse.cz> In-Reply-To: <37a28ef7-e477-40b0-a8e4-3d74b747e323@suse.cz> From: Yu Zhao Date: Sun, 27 Oct 2024 14:17:33 -0600 Message-ID: Subject: Re: [PATCH mm-unstable v2] mm/page_alloc: keep track of free highatomic To: Vlastimil Babka Cc: Andrew Morton , Johannes Weiner , Zi Yan , Mel Gorman , Matt Fleming , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Link Lin Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 8B97120004 X-Stat-Signature: cgncswkxh17ckhq599z13k7nun84wrtf X-HE-Tag: 1730060281-809063 X-HE-Meta: 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 s2h1Y/XO GrmOJYMfTpWbUXdmAYpQ6G+teC+OjCv9cX7n8Ofm1E+J/tHMFbKG4KrPo+nrGSOn/b3JB9JPJe3aOrsWlvMl9NFbDgFUohCChRM8dsMxTMhAydkOLlp5262oVdLNonjBd7AScoCeurHwX8MgxFS+KBYpOdKn8UUhdCps/8DVruXFdSVlDtp1H58q5qEjKnL32dOYfjIJdXnnkHRjYMZ6tCDlf2R00ClBoeVJO0u19CjSusRw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.002129, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, Oct 27, 2024 at 1:53=E2=80=AFPM Vlastimil Babka wr= ote: > > On 10/26/24 05:36, Yu Zhao wrote: > > OOM kills due to vastly overestimated free highatomic reserves were > > observed: > > > > ... invoked oom-killer: gfp_mask=3D0x100cca(GFP_HIGHUSER_MOVABLE), or= der=3D0 ... > > Node 0 Normal free:1482936kB boost:0kB min:410416kB low:739404kB high= :1068392kB reserved_highatomic:1073152KB ... > > Node 0 Normal: 1292*4kB (ME) 1920*8kB (E) 383*16kB (UE) 220*32kB (ME)= 340*64kB (E) 2155*128kB (UE) 3243*256kB (UE) 615*512kB (U) 1*1024kB (M) 0*= 2048kB 0*4096kB =3D 1477408kB > > > > The second line above shows that the OOM kill was due to the following > > condition: > > > > free (1482936kB) - reserved_highatomic (1073152kB) =3D 409784KB < min= (410416kB) > > > > And the third line shows there were no free pages in any > > MIGRATE_HIGHATOMIC pageblocks, which otherwise would show up as type > > 'H'. Therefore __zone_watermark_unusable_free() underestimated the > > usable free memory by over 1GB, which resulted in the unnecessary OOM > > kill above. > > > > The comments in __zone_watermark_unusable_free() warns about the > > potential risk, i.e., > > > > If the caller does not have rights to reserves below the min > > watermark then subtract the high-atomic reserves. This will > > over-estimate the size of the atomic reserve but it avoids a search. > > > > However, it is possible to keep track of free pages in reserved > > highatomic pageblocks with a new per-zone counter nr_free_highatomic > > protected by the zone lock, to avoid a search when calculating the > > It's only possible to track this reliably since the "mm: page_alloc: > freelist migratetype hygiene" patchset was merged, which explains why > nr_reserved_highatomic was used until now, even if it's imprecise. I just refreshed my memory by quickly going through the discussion around that series and didn't find anything that helps me understand the above. More pointers please?