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Wed, 24 Jul 2024 13:18:20 +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 noIPARz/oGbdEwAAD6G6ig (envelope-from ); Wed, 24 Jul 2024 13:18:20 +0000 Date: Wed, 24 Jul 2024 15:18:16 +0200 From: Petr Vorel To: Jan Kara Cc: ltp@lists.linux.it, linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-xfs@vger.kernel.org, fstests@vger.kernel.org, Jens Axboe , David Sterba , Filipe Manana , Amir Goldstein , Cyril Hrubis , Andrea Cervesato , Avinesh Kumar , Peter Zijlstra , Mike Galbraith Subject: Re: [RFC] Slow down of LTP tests aiodio_sparse.c and dio_sparse.c in kernel 6.6 Message-ID: <20240724131816.GA950793@pevik> Reply-To: Petr Vorel References: <20240719174325.GA775414@pevik> <20240722090012.mlvkaenuxar2x3vr@quack3> Precedence: bulk X-Mailing-List: linux-block@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: <20240722090012.mlvkaenuxar2x3vr@quack3> X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Action: no action X-Rspamd-Queue-Id: BEF7D1F7A1 X-Spam-Score: -3.51 X-Spam-Level: X-Spam-Flag: NO X-Spamd-Result: default: False [-3.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; HAS_REPLYTO(0.30)[pvorel@suse.cz]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; TO_DN_SOME(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[15]; MIME_TRACE(0.00)[0:+]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; FREEMAIL_CC(0.00)[lists.linux.it,vger.kernel.org,kernel.dk,suse.com,gmail.com,suse.cz,suse.de,infradead.org]; DKIM_TRACE(0.00)[suse.cz:+]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCVD_TLS_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.cz:replyto,suse.cz:dkim]; DWL_DNSWL_BLOCKED(0.00)[suse.cz:dkim]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:106:10:150:64:167:received,2a07:de40:b281:104:10:150:64:97:from]; MISSING_XM_UA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; REPLYTO_EQ_FROM(0.00)[] Hi all, [ Cc Peter and Mike ] > Hi! > On Fri 19-07-24 19:43:25, Petr Vorel wrote: > > LTP AIO DIO tests aiodio_sparse.c [1] and dio_sparse.c [2] (using [3]) > > slowed down on kernel 6.6 on Btrfs and XFS, when run with default > > parameters. These tests create 100 MB sparse file and write zeros (using > > libaio or O_DIRECT) while 16 other processes reads the buffer and check > > only zero is there. > So the performance of this test is irrelevant because combining buffered > reads with direct IO writes was always in "better don't do it" territory. > Definitely not if you care about perfomance. > > Runtime of this particular setup (i.e. 100 MB file) on Btrfs and XFS on the > > same system slowed down 9x (6.5: ~1 min 6.6: ~9 min). Ext4 is not affected. > > (Non default parameter creates much smaller file, thus the change is not that > > obvious). > But still it's kind of curious what caused the 9x slow down. So I'd be > curious to know the result of the bisection :). Thanks for report! It looks to be the slowdown was introduced by commit 63304558ba5d ("sched/eevdf: Curb wakeup-preemption") [1] from v6.6-rc1. I also compiled current next (next-20240724), it's also slow and reverting commit from it returns the original speed on both Btrfs and XFS. Kind regards, Petr [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=63304558ba5dcaaff9e052ee43cfdcc7f9c29e85 > Honza