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a=rsa-sha256; c=relaxed/relaxed; d=stgolabs.net; s=dreamhost; t=1730131547; bh=QrniIkJ7AhEemPvfI/4hebsJ2/X7SQhZHVjWmCujUIk=; h=Date:From:To:Cc:Subject:Content-Type; b=pRb6zxXTtYvDTPeG9SRZ6nbgS3wM+h/vwqna5XxL16DhjD+cPHqJlKpnqcWojhvrs LPXRom2VjmRUjkSUXcG7Qlv26c1DPM7iRxAmTQ3dFPNyRD/rJzohL9gbc/bdd3+1uz tHQFOMJKGvvA8ZRYXgFPpzW8DOKj5Ix+/lh3QbE7Z6a7IQXopvg2At6l3MQmGF7BK2 sYSVFMHak78kaUTL5UwLhtTQNaqtFPMLEY2+Tex2t3+6oDDJEJnXDLUSnDZBxX3IjN 5EbCudo97qAMcaX7r/2q8ADmTm2BVlhdm7TyaaMUBOS5sPgtqZp+lgKAuyAj/I8SPL CO2ySZXP607cQ== Date: Mon, 28 Oct 2024 09:05:43 -0700 From: Davidlohr Bueso To: Gregory Price Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com, akpm@linux-foundation.org, ying.huang@intel.com, weixugc@google.com, dave.hansen@linux.intel.com, osalvador@suse.de, shy828301@gmail.com, stable@vger.kernel.org Subject: Re: [PATCH] vmscan,migrate: fix double-decrement on node stats when demoting pages Message-ID: <20241028160543.rzx6nqsyldwocxe6@offworld> Mail-Followup-To: Gregory Price , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com, akpm@linux-foundation.org, ying.huang@intel.com, weixugc@google.com, dave.hansen@linux.intel.com, osalvador@suse.de, shy828301@gmail.com, stable@vger.kernel.org References: <20241025141724.17927-1-gourry@gourry.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20241025141724.17927-1-gourry@gourry.net> User-Agent: NeoMutt/20220429 X-Rspamd-Queue-Id: 3AB5FC0002 X-Stat-Signature: wwg5wm5xwjkhyb1i3gwaxtnnxz5pq6y9 X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1730131540-399324 X-HE-Meta: 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 RR0wO4un 3nszlR0G5KHAzwR5YubSVvI3T9AgrqlnJMiqIJ7qQmzKigKWrSdhOj1joifZeZOfOFzTQHOLMXGvYfpEfhg+i3C03aUaAwNBVDfWx7XLoGbiBz49AA04J63hUT88DDsGPbkzquDdQ50fzWttXNe1DAlGTb/z6sDp0ojHhnsOSKUvORbhpTDKxTWF0QaQo/5zcJROGOe0SOzb3Imjlh/r54ycpvPgm2c3qsNX0jm6Be9N2JXv+c33ek3f5butEnp/rkhsrs6WCsAg0Ny3Q4/B1VnOkZQ12W5ds/K/NvHt2DdhnBAE4r1aW++DnXlOGrQVQQ7yRlWuPbPMRfKUUz1+fwNQKUXUhR/CGPChN6id8QeSCy92Fn/fKvvVSewtRarE2TXQ55KehYM+zHNn/Y9fHs/0xRIrdwskUrBb1cNh434diwni0vz57z1THoQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 Fri, 25 Oct 2024, Gregory Price wrote: >When numa balancing is enabled with demotion, vmscan will call >migrate_pages when shrinking LRUs. Successful demotions will >cause node vmstat numbers to double-decrement, leading to an >imbalanced page count. The result is dmesg output like such: > >$ cat /proc/sys/vm/stat_refresh > >[77383.088417] vmstat_refresh: nr_isolated_anon -103212 >[77383.088417] vmstat_refresh: nr_isolated_file -899642 > >This negative value may impact compaction and reclaim throttling. > >The double-decrement occurs in the migrate_pages path: > >caller to shrink_folio_list decrements the count > shrink_folio_list > demote_folio_list > migrate_pages > migrate_pages_batch > migrate_folio_move > migrate_folio_done > mod_node_page_state(-ve) <- second decrement > >This path happens for SUCCESSFUL migrations, not failures. Typically >callers to migrate_pages are required to handle putback/accounting for >failures, but this is already handled in the shrink code. > >When accounting for migrations, instead do not decrement the count >when the migration reason is MR_DEMOTION. As of v6.11, this demotion >logic is the only source of MR_DEMOTION. > >Signed-off-by: Gregory Price >Fixes: 26aa2d199d6f2 ("mm/migrate: demote pages during reclaim") >Cc: stable@vger.kernel.org Reviewed-by: Davidlohr Bueso