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Wed, 2 Sep 2026 12:25:22 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id hMeqJ7IVmGqjFgAAD6G6ig (envelope-from ); Wed, 02 Sep 2026 12:25:22 +0000 Date: Wed, 2 Sep 2026 14:25:30 +0200 From: Cyril Hrubis To: Nirmoy Das Message-ID: References: <20260825152544.1675541-1-nirmoyd@nvidia.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20260825152544.1675541-1-nirmoyd@nvidia.com> X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCPT_COUNT_TWO(0.00)[2]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.cz:email,imap1.dmz-prg2.suse.org:helo] X-Virus-Scanned: clamav-milter 1.0.9 at in-6.smtp.seeweb.it X-Virus-Status: Clean Subject: Re: [LTP] [RFC PATCH] getrusage03: account for percpu RSS counter batching X-BeenThere: ltp@lists.linux.it X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux Test Project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ltp@lists.linux.it Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ltp-bounces+ltp=archiver.kernel.org@lists.linux.it Sender: "ltp" Hi! > getrusage03 allows ru_maxrss to differ from the expected value by a > fixed 20 MiB. That can be too small on large systems after Linux commit > f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter"). > > The fast RSS read may miss percpu counter batches, and the batch size > scales with the number of online CPUs. The test child is single threaded, > but it can migrate while faulting memory, so allow two batches worth of > slack based on the online CPU count and page size. Keep the existing > 20 MiB floor for smaller systems. > > This is sent as RFC because it makes the test tolerate Linux's current > percpu counter batching behavior instead of treating the smaller > ru_maxrss value as a kernel failure. Maybe we can pin the whole test to a single CPU instead. Otherwise the max rss delta can easily get into hundreds of megabytes, which is more than the test consumes. -- Cyril Hrubis chrubis@suse.cz -- Mailing list info: https://lists.linux.it/listinfo/ltp