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Mon, 21 Oct 2024 10:11:30 -0700 (PDT) MIME-Version: 1.0 References: <20241020051315.356103-1-yuzhao@google.com> In-Reply-To: From: Yu Zhao Date: Mon, 21 Oct 2024 11:10:50 -0600 Message-ID: Subject: Re: [PATCH mm-unstable v1] mm/page_alloc: try not to overestimate free highatomic To: Michal Hocko Cc: Andrew Morton , 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-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: D885D20011 X-Stat-Signature: e161d5eyiephqk7xaz6fnj4aexamnmer X-HE-Tag: 1729530675-789439 X-HE-Meta: U2FsdGVkX19P+PL/yk/REaCiTNl116fEGVoSHzCQJXiUrSCLVSXmhY1iYNBuJ2kx0U2AYdkyzbfkGaBMaoInxrFhTAOzcMU1WSpG0RNq0GT7JpCoDpNLGO+MHwJfRX8oHEDRafEBNQEtEUbOnZEAP5V9dcHcCDWFafUTuuiTMSShF/ba5vctUdzudHaKEnZT43p1FgE9C7a8gajH4BCAo3x+IdcqGHwQ6Xo+tBYVGxSFXFI8C9D7HlLnoUz0+UipYFmDvSL0BwhPLo1bQ/kEdPh13NN1J28UnwZqHUrA0vgBJUtLxgdzfrbk+Q3dZ+Wc5oncS6dupUuW0eRB5mWRwAMDKEjV1HQnmtqTwYWCvJGzVr7XM8dI+ouThyhe/p8M+1zE9nMqseoGah9C9oRWxHtl0ek/eTMaBqA14qRo819qZnnO0hxIQQCcfeFDybZAlUK7fGwoWmpdtYPMs+NBfMiFcWsIY5T+WIrQVbw2Bgy7sBHmzb3tfUPvj2TirD4mv9WmYt5Dkg4ElpYisR0FM3+2oeusjupbnjjGO8Yrb1CfxFOUzeC5aaf4BoVuCOHw4CFPbLHNpfimpV3TbQ3VtKv6EKBe4einL0BxsbTiq2xTbQpXbJrWBtqPUl2pG6ZgEX4Smem/Qy4RO0kXn4VRr+gO1VkH9YWynoe4d6pRm7prcj9QMuycy/O/mMTqlRuhqgaGYjZv4rMQ/BVF/AHhrXyxhZiFr0G9HW0M0sN45251FHWDsnhumCW2L/QeaLgtdK1+jNexTyo/VGVlUpzVIeg91nveHXQWw9cLlOPBoW1pCCMd1henHJ2x3MyQEe3thOyACaORFtWTeLFjB6KNglVGzv4h+CFDJ4WO+xr9NMgZv8lq8H74AvlW9AQDxIG/q3ZNbfguk5mMkqWlMPEjJHqGPlY0w5ujfdzwZcC7bchkImrcaO5o4QTXH7xmT6/DKPkUyxGUNSFQJx2DcZF I0E/ypYQ WJ9GDQM0RCzAOqSHzPWq32xqwNzLyMJLFr3+oZHz1xOP4pns+NG7wq0jV3w5p/s9pOZCc1sUIxhmonBVLXhsmnYw7jt9TaAjSL2NGgzM2Ud2amXW5s0PK992Da+eUG8a3xZ4sWx1GaEZGnzroZ6HRfMeYsWmlGfZN9zgg7VOtBPVLdFZzQnFMb+UHGQqM0nSlrIYW95oIQ38Sxws1Ftq3WuQMkancOF9QqzrGHP03NXYwkxSs8sHjYEqRHLJ7z6aMw99u1CY07ggEd7U3LjoK+2W60jiPq+EFQH11Mm4ONsgFzA8= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000255, 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 Mon, Oct 21, 2024 at 2:13=E2=80=AFAM Michal Hocko wrot= e: > > 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=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() 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? The current behavior of unreserve_highatomic_pageblock() seems WAI to me: it unreserves highatomic pageblocks that contain *free* pages so that those pages can become usable to others. There is nothing to unreserve when they have no free pages.