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 X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 930FDC43381 for ; Thu, 7 Mar 2019 15:07:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 62EF320835 for ; Thu, 7 Mar 2019 15:07:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726361AbfCGPHT (ORCPT ); Thu, 7 Mar 2019 10:07:19 -0500 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:59224 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726224AbfCGPHS (ORCPT ); Thu, 7 Mar 2019 10:07:18 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R741e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04392;MF=shile.zhang@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0TMBVIKI_1551971208; Received: from ali-6c96cfdd1403.local(mailfrom:shile.zhang@linux.alibaba.com fp:SMTPD_---0TMBVIKI_1551971208) by smtp.aliyun-inc.com(127.0.0.1); Thu, 07 Mar 2019 23:06:57 +0800 Subject: Re: [PATCH] bcache: add cond_resched() in __bch_cache_cmp() To: Coly Li Cc: Kent Overstreet , linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org References: <1551935728-243664-1-git-send-email-shile.zhang@linux.alibaba.com> <24916a71-39ff-7324-ad12-9d79cc68d0da@suse.de> From: Shile Zhang Message-ID: <3640cd7f-f32a-1509-dbef-6000b6e14e75@linux.alibaba.com> Date: Thu, 7 Mar 2019 23:06:47 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <24916a71-39ff-7324-ad12-9d79cc68d0da@suse.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/3/7 18:34, Coly Li wrote: > On 2019/3/7 1:15 下午, shile.zhang@linux.alibaba.com wrote: >> From: Shile Zhang >> >> Read /sys/fs/bcache//cacheN/priority_stats can take very long >> time with huge cache after long run. >> >> Signed-off-by: Shile Zhang > Hi Shile, > > Do you test your change ? It will be helpful with more performance data > (what problem that you improved). In case of 960GB SSD cache device, once read of the 'priority_stats' costs about 600ms in our test environment. The perf tool shown that near 50% CPU time consumed by 'sort()', this means once sort will hold the CPU near 300ms. In our case, the statistics collector reads the 'priority_stats' periodically, it will trigger the schedule latency jitters of the task which shared same CPU core. > > Thanks. > > Coly Li > >> --- >> drivers/md/bcache/sysfs.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c >> index 557a8a3..028fea1 100644 >> --- a/drivers/md/bcache/sysfs.c >> +++ b/drivers/md/bcache/sysfs.c >> @@ -897,6 +897,7 @@ static void bch_cache_set_internal_release(struct kobject *k) >> >> static int __bch_cache_cmp(const void *l, const void *r) >> { >> + cond_resched(); >> return *((uint16_t *)r) - *((uint16_t *)l); >> } >> >> >