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 91A85C433DB for ; Fri, 5 Mar 2021 09:01:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 49C4664EE8 for ; Fri, 5 Mar 2021 09:01:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229599AbhCEJBX (ORCPT ); Fri, 5 Mar 2021 04:01:23 -0500 Received: from mout.gmx.net ([212.227.17.22]:40515 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229672AbhCEJA7 (ORCPT ); Fri, 5 Mar 2021 04:00:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1614934857; bh=igxj5LgMmYbcBIHKFR3fz4BAwGgmoVOuqlu3GD1Rk2A=; h=X-UI-Sender-Class:Subject:To:Cc:References:From:Date:In-Reply-To; b=MGSzemqWITYMQwJxB9dZVs96BKWtzJXyAvmuBY9r4FQ+92L16QVfEVTuD8XveX9Lz 69+L2f2Vg90u15AjFiIoPrQ+OKfS/SjdjYSFcPFMy4VHYy3CpPUNJNXV8jP4kCYj5A t+ZZbKh/VMOz/uXw0C4hi2h6CzdRKFheJYfbth80= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [10.10.25.85] ([103.52.188.137]) by mail.gmx.net (mrgmx104 [212.227.17.174]) with ESMTPSA (Nemesis) id 1Mv2xU-1lZUgi20WG-00qzsV; Fri, 05 Mar 2021 10:00:57 +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: <91cf3980-ed9d-a5f8-4f2d-d9a79b1cbed0@gmx.com> Date: Fri, 5 Mar 2021 17:00:53 +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:ipOUIE5i5zm5oB2dKflm+ce+569Uh+Gu6LkZVLykciAjgdgmx7J gdV0J1QFVZ5qT8GyKDnoDP/SmemLmM582w6o/K20Mne+LX6pNa9Nj1BW8tFHQiV9rOaWbCF MLNfVVsIoKl4PgJDebzwfIN0dy0fmOaLehdlX9W6dsc81F+iZ78VXPCW3Z2lLaWgfia3CZT yzNwPADxpHJY5ZGuRUV5Q== X-UI-Out-Filterresults: notjunk:1;V03:K0:oqGFe+d6zw8=:pUnyUfGE59xjjD/GIvNcQU FeqUjTzbMSXBQ3yH9BdSNwBPU0ABa5cExF3TuEtyuNSxLgcESKhkYD13DxgoiJ9KhSMttXPxJ jpLMF7sf69F7Le/v0N9DDKSSPGK7zPD7XyA8fkmxBOkaOoDL2J7KgfmSUM6Vqpujh79zpxeNA 8C12e87NfRjekRH/UZ3f66eLHVh5aCYr1PBsqjO/aghD5YAHSu2vpronYim9SGSln7sxAugT/ v65r/w7aGQlVzjwUm7TLghOEHlW9Hy0AuHeNM0BgDzdv0/PDzZKTTS+zqJhS+cwQZp9z0k6DO o8Ogiz4I4NcaCoYs7wPQwyG2fFZJGO8/JrIrlKTLtc/Npf5Y+zSi0FYYqZGOIr+OWH1LEQGwk iHZKOmxS1Lb47IaCAp8WshuyIBJw7vhLifYAf5Yuh0W8ZS+df6w7gPn/pchPr+dBINWf8p374 oIwgy/W02K6YWottIrOw9GMeK1Kr3JH9c27h7xnIe6MhGQXBIxCkL+fB4h2QWlzVt3NPJrTed qUWVisWin4L4YwSjoAadqGDyE4PH7QcTIuKMBKCL5/kftRYfUDy/sBXO5yjVlMPY71s1DW41V DlANxhci89pNQp7/zvXgECKrDw//HM7c4jDGEH/rU1kG810z1rJy4r7Ru/TIu3vtH/hv/OBCw AMdk11UWL5P2CAot5+vqVELxksPqA1bJK6qqoB0ZYM++QS3QmisSo2Xd4QPzeTDSu7KrzBMo+ 3gsanqZKP0zWfTj/aIkFdQ1NrZ1WAhDHe2qxEDfB+iJrzDiwY+Ghm6sPYCefI/th//GOUyaii 63kq6bKOJex6wpLFHEk9gVVuG2uwQNyvuGrXpS1vYha1wp9CA54OI7uBBMthKPYNjz9tK52W4 0P18kufEdoGgVt0Jet6g== 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 have test on 5.8.X,=C2=A0 but it doesn't help. I test on the same config= on another server(480G SSD + 8T HDD), it can't reproduce, this really made me confused. I will compare the confi= gs and try to find out the diffs. Thanks. Norman > > Thanks. > > Coly Li