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=-2.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 6F5CBC433E6 for ; Wed, 3 Mar 2021 15:59:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1FB8064EE4 for ; Wed, 3 Mar 2021 15:59:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231731AbhCCPyj (ORCPT ); Wed, 3 Mar 2021 10:54:39 -0500 Received: from mout.gmx.net ([212.227.17.20]:58413 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242396AbhCCD2O (ORCPT ); Tue, 2 Mar 2021 22:28:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1614741941; bh=Dbl45cYffM5VpBIUPk3aPwijqlx22eo8BibXzeyHTpA=; h=X-UI-Sender-Class:Subject:To:Cc:References:From:Date:In-Reply-To; b=FFJZU9w878QZNIgGE7AIcB530Gb8uX2kHutABSkzBx1ImYEUrLAuiRwZ9bh/KvlRI qe4xMgD7EMul1aASa5um6GKcvQXZkN63MiIFH4HAkXI+bruYnvFls9Fk9sbI6HPgkc cDfB085t7yVxNM7pLV2yBmVNn1a0oy3lCNUaCWlU= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [10.10.213.91] ([103.52.188.137]) by mail.gmx.net (mrgmx104 [212.227.17.174]) with ESMTPSA (Nemesis) id 1MSKu0-1lO0Fg34A4-00ScLs; Wed, 03 Mar 2021 04:25:41 +0100 Subject: Re: Large latency with bcache for Ceph OSD(new mail thread) To: Coly Li Cc: linux-bcache@vger.kernel.org, linux-block@vger.kernel.org References: <9b7dfd49-67b0-53b1-96e1-3b90c2d9d09a@gmx.com> From: "Norman.Kern" Message-ID: Date: Wed, 3 Mar 2021 11:25:37 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US X-Provags-ID: V03:K1:WhGy41qMcy29eNrypJcrubMAdwVFszEDZZ8RDJx8QZTR6ZVQmXW JKXNrJO8AnRBfnBMrgcrqGSQeCiwcgFWISrnP+qfAzQtJTiUnZ+YvMCuLpDaGbXPnUTjWEb 9TgUDZD1X6CZTpoilFMDnAtQvueMlMNPWLlfRYbx/tKiiK4JfzTAxAkYiIMyiFmkXajbY+u MLJoFp+e8NC0NU4hmcHRg== X-UI-Out-Filterresults: notjunk:1;V03:K0:RR+Ia3bucGc=:kyBnJsTtx7xZoGvLiFalEs uOYgqdU/7UHXhYXYE2Wz/sPeNgoGOdkR6n7uHGZUcMgJn19TeWjMok/iBHdZNCAnXgnZ/jceN uPPB3C2cVR+O7WOXKJrk6TZ7R9EKRtPrOFWFhuYOlSI7FN+Rq9ArIm39kQNlv1rH6tmbgt7g0 lmTFdQe7F23lvamu5u3zWpt7jHGSmgEtMbZVZw9uWwvO6iErXpMSnXvW0IRq/L5PHbF6lJzn+ 6zy4AFoY6Qqr0+JxNNK/hD7BmQjZEfzJSQonKFC3eDLrRayk84PTXoAX9FUkeo5sglqPWqLjm OaGMCDsvHr5wyUUYlFsoN2owXa2mUXef0ksBdcwIKjR9+pD/0QXnhNMI/QpO7HO61WrWyEH7p 7r5HMkFUPN9Nn3H+hQPbKzei5F7zTWYs61aqH/T40RMucDgxy4KwFHwE2w4BUR8gt6H1YdnHd eyYqBGEapU8fFmZDeRfeaphuNFkfkryiSTDuuFwgHQ926lm+XDvuy1+xFeyV+oMOpuaykD2kL OMVdkydCx1EPHOk2BJ5Qc6kvex4GyexTaKxJ8r4UAg5yDRcMYM/gK8Ho6+9nwGtcqBEAykIhc T+xH3i+Se9ygdKwxGYKktXffz/VkVijz/91MalgEF2mD3SZKLrlktlFsUiMcci1Hs7brjvRb9 Nf0HyJQ1liJFE11ESpS9Yb8+UEq3flDzJW/aLA20h1rqAFU21VPig822SjbkNCpMNm4b3RD5e htmP0AsT1e5V1StiRWc2lrz2D61ub+csRlSphkMZMF1oAsOodn+NzpbiPrt4J9QpplBLZbzOo 91kTdMHVVxGdJNLy12W1+ihWCo6QHFFiLPnSu62d/E9bsK4Njql+yeShmuU51K+WSXdYuYtQ7 +/hNzUKCCrcyYSVWlzZQ== Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org On 2021/3/2 =E4=B8=8B=E5=8D=889:20, Coly Li wrote: > On 3/2/21 6:20 PM, Norman.Kern wrote: >> Sorry for creating a new mail thread(the origin is so long...) >> >> >> I made a test again and get more infomation: >> >> root@WXS0089:~# cat /sys/block/bcache0/bcache/dirty_data >> 0.0k >> root@WXS0089:~# lsblk /dev/sda >> NAME=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 MAJ:MIN RM=C2=A0=C2=A0 SIZE RO TYPE = MOUNTPOINT >> sda=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 8:0=C2=A0=C2=A0=C2= =A0 0 447.1G=C2=A0 0 disk >> `-bcache0 252:0=C2=A0=C2=A0=C2=A0 0=C2=A0 10.9T=C2=A0 0 disk >> root@WXS0089:~# cat /sys/block/sda/bcache/priority_stats >> Unused:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 1% >> Clean:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 29% >> Dirty:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 70% >> Metadata:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0% >> Average:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 49 >> Sectors per Q:=C2=A0 29184768 >> Quantiles:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 [1 2 3 5 6 8 9 11 13 14 16 19 = 21 23 26 29 32 36 39 43 48 53 59 65 73 83 94 109 129 156 203] >> root@WXS0089:~# cat /sys/fs/bcache/066319e1-8680-4b5b-adb8-49596319154b= /internal/gc_after_writeback >> 1 >> You have new mail in /var/mail/root >> root@WXS0089:~# cat /sys/fs/bcache/066319e1-8680-4b5b-adb8-49596319154b= /cache_available_percent >> 28 >> >> I read the source codes and found if cache_available_percent > 50, it s= hould wakeup gc while doing writeback, but it seemed not work right. >> > If gc_after_writeback is enabled, and after it is enabled and the cache > usage > 50%, a tag BCH_DO_AUTO_GC will be set to c->gc_after_writeback. > Then when the writeback completed the gc thread will wake up in force. > > so the auto gc after writeback will be triggered when, > 1, the bcache device is in writeback mode > 2, gc_after_writeback set to 1 > 3, After 2) done, the cache usage exceeds 50% threshold. > 4, writeback rate set to maximum rate when the bcache device is idle (no > regular I/O request) > 5, after the writeback accomplished, the gc thread will be waken up. > > But /sys/block/bcache0/bcache/dirty_data is 0.0k doesn't mean the > writeback is accomplished. It is possible the writeback thread still > goes through all btree keys for the last try even all the dirty data are > flushed. Therefore you should check whether the writeback thread is > still active before a conclusion is made that the writeback is completed= . > > BTW, do you try a Linux v5.8+ kernel and see how things are ? I stoped all rw tests for almost the whole day and no iops from iostat. Wh= en I echo 1 to trigger_gc the cache_available_percent changed for 29 to 100 in seconds. I will have a test on 5.8.0-44. > > Thanks. > > Coly Li