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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 6D9E0C34022 for ; Wed, 19 Feb 2020 03:54:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3C0D0206DB for ; Wed, 19 Feb 2020 03:54:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726512AbgBSDyh (ORCPT ); Tue, 18 Feb 2020 22:54:37 -0500 Received: from szxga07-in.huawei.com ([45.249.212.35]:58866 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726439AbgBSDyh (ORCPT ); Tue, 18 Feb 2020 22:54:37 -0500 Received: from DGGEMS407-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 2E7D78F300AE887A7AEF; Wed, 19 Feb 2020 11:54:34 +0800 (CST) Received: from [10.134.22.195] (10.134.22.195) by smtp.huawei.com (10.3.19.207) with Microsoft SMTP Server (TLS) id 14.3.439.0; Wed, 19 Feb 2020 11:54:28 +0800 Subject: Re: [f2fs-dev] [PATCH 3/3] f2fs: skip migration only when BG_GC is called To: Jaegeuk Kim CC: , References: <20200214185855.217360-1-jaegeuk@kernel.org> <20200214185855.217360-3-jaegeuk@kernel.org> <9c497f3e-3399-e4a6-f81c-6c4a1f35e5bb@huawei.com> <20200218232714.GB10213@google.com> <117a927f-7128-b5a1-a961-22934bb62ec5@huawei.com> <20200219030425.GA102063@google.com> From: Chao Yu Message-ID: <266f233b-e084-cccd-d07e-96d8438d5b74@huawei.com> Date: Wed, 19 Feb 2020 11:54:28 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200219030425.GA102063@google.com> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/2/19 11:04, Jaegeuk Kim wrote: > On 02/19, Chao Yu wrote: >> On 2020/2/19 7:27, Jaegeuk Kim wrote: >>> On 02/17, Chao Yu wrote: >>>> On 2020/2/15 2:58, Jaegeuk Kim wrote: >>>>> FG_GC needs to move entire section more quickly. >>>>> >>>>> Signed-off-by: Jaegeuk Kim >>>>> --- >>>>> fs/f2fs/gc.c | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c >>>>> index bbf4db3f6bb4..1676eebc8c8b 100644 >>>>> --- a/fs/f2fs/gc.c >>>>> +++ b/fs/f2fs/gc.c >>>>> @@ -1203,7 +1203,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi, >>>>> >>>>> if (get_valid_blocks(sbi, segno, false) == 0) >>>>> goto freed; >>>>> - if (__is_large_section(sbi) && >>>>> + if (gc_type == BG_GC && __is_large_section(sbi) && >>>>> migrated >= sbi->migration_granularity) >>>> >>>> I knew migrating one large section is a more efficient way, but this can >>>> increase long-tail latency of f2fs_balance_fs() occasionally, especially in >>>> extreme fragmented space. >>> >>> FG_GC requires to wait for whole section migration which shows the entire >>> latency. >> >> That will cause long-tail latency for single f2fs_balance_fs() procedure, >> which it looks a very long hang when userspace call f2fs syscall, so why >> not splitting total elapsed time into several f2fs_balance_fs() to avoid that. > > Then, other ops can easily make more dirty segments. The intention of FG_GC is Yup, that's a problem, if there are more dirty datas being made, reserved segments may be ran out during FG_GC. > to block everything and make min. free segments as a best shot. I just try to simulate write GC's logic in FTL to mitigate single op's max latency, otherwise benchmark looks hang during FG_GC (in a 500mb+ section). Thanks, > >> >> Thanks, >> >>> >>>> >>>> Thanks, >>>> >>>>> goto skip; >>>>> if (!PageUptodate(sum_page) || unlikely(f2fs_cp_error(sbi))) >>>>> >>> . >>> > . >