From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from picard.linux.it (picard.linux.it [213.254.12.146]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A5511D13C3E for ; Mon, 26 Jan 2026 15:46:07 +0000 (UTC) Received: from picard.linux.it (localhost [IPv6:::1]) by picard.linux.it (Postfix) with ESMTP id 056A33C6221 for ; Mon, 26 Jan 2026 16:46:06 +0100 (CET) Received: from in-7.smtp.seeweb.it (in-7.smtp.seeweb.it [217.194.8.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (secp384r1)) (No client certificate requested) by picard.linux.it (Postfix) with ESMTPS id 4F8913C0322 for ; Mon, 26 Jan 2026 16:45:48 +0100 (CET) Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by in-7.smtp.seeweb.it (Postfix) with ESMTPS id D5FF72001A2 for ; Mon, 26 Jan 2026 16:45:47 +0100 (CET) Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 557B533689; Mon, 26 Jan 2026 15:45:47 +0000 (UTC) Authentication-Results: smtp-out1.suse.de; none Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 3CD73139E9; Mon, 26 Jan 2026 15:45:47 +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 ztifDSuMd2nObAAAD6G6ig (envelope-from ); Mon, 26 Jan 2026 15:45:47 +0000 Date: Mon, 26 Jan 2026 16:47:02 +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-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Rspamd-Action: no action X-Rspamd-Queue-Id: 557B533689 X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spamd-Result: default: False [-4.00 / 50.00]; REPLY(-4.00)[] X-Virus-Scanned: clamav-milter 1.0.9 at in-7.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! > This is definetly a possible solution. I sent this patch by waiting for > some feebacks in order to have other opinions. What puzzles me is that > it's only happening in POWER10 on a random node during kernel tests. > Other architectures seem to work fine. > > kernel 6.6+ seems to be the affected one. > > > > > However the test should finish as fast as the writer finishes writing > > the file. So slow readers shouldn't matter unless there is some serious > > contention on the disk I/O. That's probably the reason you are aligning > > the writer as well. > > Exactly, I would expect that. > > > > > What is the difference in runtime between test before and after this > > patch on the slow hardware? > > DS009 from 4 hours to 30 seconds. I also profiled the list of syscalls > with perf, obtaining a 63+ % of io_read() time consumption. Still, this > patch moves the execution from ~10 secs to ~3 secs on my laptop. There's > a big difference between 4h and 10 secs runtime, no matter the hard disk > which is running below. Honestly that does sound like a kernel bug. You shouldn't get several orders of magnitude slower just because your buffer is 4 times smaller. -- Cyril Hrubis chrubis@suse.cz -- Mailing list info: https://lists.linux.it/listinfo/ltp