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Mon, 26 Jan 2026 11:43:13 +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 800VMFFTd2nzZAAAD6G6ig (envelope-from ); Mon, 26 Jan 2026 11:43:13 +0000 Date: Mon, 26 Jan 2026 12:44:32 +0100 From: Cyril Hrubis To: Andrea Cervesato Message-ID: References: <20260126-fix_dio_sparse_slow-v2-1-5dbe1622f5c1@suse.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: 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]; RCVD_VIA_SMTP_AUTH(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; ARC_NA(0.00)[]; MISSING_XM_UA(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]; TO_DN_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; MIME_TRACE(0.00)[0:+]; 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-Virus-Scanned: clamav-milter 1.0.9 at in-2.smtp.seeweb.it X-Virus-Status: Clean Subject: Re: [LTP] [PATCH v2] io: fix really slow dio_sparse on certain systems 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: Linux Test Project 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! > I guess it's not about slow buffering. What I suppose happens is that > every time the writer thread writes with O_DIRECT it invalidates the > page cache and we have to re-read everything from disk. Which measn that > the data are often removed from the cache between the reads and the > reader processes are often forced to re-read the data from the disk. If > there was no O_DIRECT reader thread the first child that happens to read ^ writer -- Cyril Hrubis chrubis@suse.cz -- Mailing list info: https://lists.linux.it/listinfo/ltp