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Thu, 18 Jun 2026 16:32:33 +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 QS63BqEdNGo4GAAAD6G6ig (envelope-from ); Thu, 18 Jun 2026 16:32:33 +0000 Date: Thu, 18 Jun 2026 17:32:31 +0100 From: Pedro Falcato To: Suren Baghdasaryan Cc: Lorenzo Stoakes , Jan Kara , kernel test robot , Frederick Mayle , oe-lkp@lists.linux.dev, lkp@intel.com, Andrew Morton , Kalesh Singh , David Hildenbrand , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [linux-next:master] [mm] 7b32f64bc5: pts.svt-av1.Preset13.Bosphorus4K.frames_per_second 45.8% regression Message-ID: References: <202606181547.617a6967-lkp@intel.com> <6z2rqmo7b6m2rdhqurspwya25ps4dj7lctdygnmq3rn4xt6h3i@57kiiy72epgd> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Spam-Flag: NO X-Spam-Score: -3.80 X-Spamd-Result: default: False [-3.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_TWELVE(0.00)[13]; MISSING_XM_UA(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de: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)[imap1.dmz-prg2.suse.org:helo] X-Spam-Level: On Thu, Jun 18, 2026 at 04:03:43PM +0000, Suren Baghdasaryan wrote: > On Thu, Jun 18, 2026 at 2:30 PM Lorenzo Stoakes wrote: > > > > On Thu, Jun 18, 2026 at 11:30:47AM +0200, Jan Kara wrote: > > > On Thu 18-06-26 16:00:42, kernel test robot wrote: > > > > Hello, > > > > > > > > kernel test robot noticed a 45.8% regression of pts.svt-av1.Preset13.Bosphorus4K.frames_per_second on: > > > > > > This one looks serious enough and real. It would be good to figure out what > > > happens in this benchmark that it benefits from the readahead across VMA > > > boundaries so much... > > > > I think a revert first no? This seems pretty huge for something that isn't key > > to the kernel, then a new attempt can be tried with this issue addressed > > perhaps? > > A quick search yields: "The > pts.svt-av1.Preset13.Bosphorus4K.frames_per_second is a benchmarking > metric from the Phoronix Test Suite that measures how many frames per > second a CPU can encode using the open-source SVT-AV1 video encoder." > > If this is a video encoding benchmark I would expect it to explicitly > prefetch the data from the disk before measuring the encoding speed. > If limiting readahead caused this regression, I suspect the benchmark > doesn't explicitly prefetch the data... Well, commonly video data doesn't actually fit in memory :) A quick look at the code (I think it's https://gitlab.com/AOMediaCodec/SVT-AV1/-/blob/master/Source/App/app_process_cmd.c#L821) suggests it is progressively mapping the file data for a given frame (or frames?). So the old behavior would result in page faults for a given frame starting readahead for the next few frames. This looks reasonable. FWIW I suspected this was a really weird case regarding mprotect or something, and I'm happy it isn't; but at least I had a suggestion for that - for this, maybe dropping the change (for now?) is the best course of action. -- Pedro