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[109.81.89.238]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a9a91370631sm173355166b.104.2024.10.21.01.13.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Oct 2024 01:13:34 -0700 (PDT) Date: Mon, 21 Oct 2024 10:13:33 +0200 From: Michal Hocko To: Yu Zhao Cc: Andrew Morton , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Link Lin Subject: Re: [PATCH mm-unstable v1] mm/page_alloc: try not to overestimate free highatomic Message-ID: References: <20241020051315.356103-1-yuzhao@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241020051315.356103-1-yuzhao@google.com> On Sat 19-10-24 23:13:15, Yu Zhao wrote: > OOM kills due to vastly overestimated free highatomic reserves were > observed: > > ... invoked oom-killer: gfp_mask=0x100cca(GFP_HIGHUSER_MOVABLE), order=0 ... > 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 = 1477408kB > > The second line above shows that the OOM kill was due to the following > condition: > > free (1482936kB) - reserved_highatomic (1073152kB) = 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() overestimated free > highatomic reserves. IOW, it underestimated the usable free memory by > over 1GB, which resulted in the unnecessary OOM kill. Why doesn't unreserve_highatomic_pageblock deal with this situation? -- Michal Hocko SUSE Labs