Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751688AbbDAE7L (ORCPT ); Wed, 1 Apr 2015 00:59:11 -0400 Received: from mga09.intel.com ([134.134.136.24]:44014 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750748AbbDAE7K (ORCPT ); Wed, 1 Apr 2015 00:59:10 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.11,503,1422950400"; d="scan'208";a="673536432" Message-ID: <1427864347.17170.105.camel@intel.com> Subject: Re: [LKP] [Btrfs] 3a8b36f3780: -62.6% fileio.requests_per_sec From: Huang Ying To: Filipe Manana Cc: Chris Mason , LKML , LKP ML Date: Wed, 01 Apr 2015 12:59:07 +0800 In-Reply-To: <551AB664.4080303@suse.com> References: <1426666837.5570.36.camel@intel.com> <55094E06.2070004@suse.com> <1427790767.17170.95.camel@intel.com> <551AB664.4080303@suse.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.9-1+b1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2136 Lines: 56 On Tue, 2015-03-31 at 15:59 +0100, Filipe Manana wrote: [snip] > From: Filipe Manana > Date: Tue, 31 Mar 2015 14:16:52 +0100 > Subject: [PATCH] Btrfs: avoid syncing log in the fast fsync path when not > necessary > > Commit 3a8b36f37806 ("Btrfs: fix data loss in the fast fsync path") added > a performance regression for that causes an unnecessary sync of the log > trees (fs/subvol and root log trees) when 2 consecutive fsyncs are done > against a file, without no writes or any metadata updates to the inode in > between them and if a transaction is committed before the second fsync is > called. > > Huang Ying reported this to lkml after a test sysbench test that measured > a -62% decrease of file io requests for that tests' workload. > > The test is: > > echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor > echo performance > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor > echo performance > /sys/devices/system/cpu/cpu2/cpufreq/scaling_governor > echo performance > /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor > mkfs -t btrfs /dev/sda2 > mount -t btrfs /dev/sda2 /fs/sda2 > cd /fs/sda2 > for ((i = 0; i < 1024; i++)); do fallocate -l 67108864 testfile.$i; done > sysbench --test=fileio --max-requests=0 --num-threads=4 --max-time=600 \ > --file-test-mode=rndwr --file-total-size=68719476736 --file-io-mode=sync \ > --file-num=1024 run > > A test on kvm guest, running a debug kernel gave me the following results: > > Without 3a8b36f378060d: 16.01 reqs/sec > With 3a8b36f378060d: 3.39 reqs/sec > With 3a8b36f378060d and this patch: 16.04 reqs/sec > > Reported-by: Huang Ying I have tested your patch, the regression restored in our test. Thanks! Tested-by: Huang, Ying Best Regards, Huang, Ying [snip] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/