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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B76AC77B7C for ; Sun, 7 May 2023 15:32:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231516AbjEGPci (ORCPT ); Sun, 7 May 2023 11:32:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34396 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229472AbjEGPch (ORCPT ); Sun, 7 May 2023 11:32:37 -0400 Received: from mail-pg1-x530.google.com (mail-pg1-x530.google.com [IPv6:2607:f8b0:4864:20::530]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 99C991BF3 for ; Sun, 7 May 2023 08:32:11 -0700 (PDT) Received: by mail-pg1-x530.google.com with SMTP id 41be03b00d2f7-52c6f8ba7e3so3365482a12.3 for ; Sun, 07 May 2023 08:32:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1683473531; x=1686065531; h=content-transfer-encoding:in-reply-to:from:references:cc:to:subject :user-agent:mime-version:date:message-id:from:to:cc:subject:date :message-id:reply-to; bh=hAJuFKA2WbO5t/MWWkp+wgsDKDGBHsZX3U7rMhZW364=; b=UpbnHFU0yNMCgNV9dnHl4cjW83awcatKcDRhy2ig6Ca5S9Z3M94my+SMkCOVeNFnTl RAQfynxmMy0N2iLYGLBm5Az1588DhsKr6umonO9iVsKIg4VskyU0ABt3asFM4iEdqmr6 uTHJsBxh4dFRGoxgZFmA7YNRcXzrdpD9P/dyvHQTmjSiC0dl2LutRFA0d7RsKavWGiNR WwNFi73Hd1VzqbCbKaO5MSTkw1+nIXtIfdlquAe0Mz+PmgvH3ZCetgaMwxwgxaCkn3Gf 7BKZH0oX19hHHZ6TLmtytJ/cRW2hMBWKyRsaBKsFcwdNszfw9hY60KQq/B79zbfVUnHm Ybeg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1683473531; x=1686065531; h=content-transfer-encoding:in-reply-to:from:references:cc:to:subject :user-agent:mime-version:date:message-id:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=hAJuFKA2WbO5t/MWWkp+wgsDKDGBHsZX3U7rMhZW364=; b=Ngs5b8PzJSkApIcLVje7ziWMEE/GYp3Zo0Rx973tdTHGIpPQiNqAHp9j8A8jT/zn2M hzDGihkm7iFuHZUZ5YHYBTruXK+0QFnH43nD93oEmvBh94WBfrnWCYqPSiJiD8i/KkRn iy1FpqdZVJS6OzTnJuZxsLgqTqjrBprzbL61SAI0zzTsdPd3/0caVOc6ht0Ouo+hMzH8 4r37x28pvfWjMtH97Kp7tXFRcPZHQapJGHARDZfxRbcC2By+VhW3OkCa5hx3OJY4Nfhl gOJVA+2QaHFnAFUfNXzgJY1+bINy6y2z5vR5k3+ZYjMF3XO2D5S7JXa0LS7dLCJX42GO C0Rw== X-Gm-Message-State: AC+VfDyJY3IrcGHwcxNncxsMUaAwPH0NRM85MXCLrAKdMuEW2gG9PsOu LFyqkp1XKftkXpuq8RnJ0R/7Sg== X-Google-Smtp-Source: ACHHUZ5vaZYny/4Xt5w97TuH6E7aN33rhIjuGoHCPKDMntXPppnOmvCAE8+RUtWWpI3C0dGcV61hZg== X-Received: by 2002:a17:902:6b86:b0:1a2:9183:a49c with SMTP id p6-20020a1709026b8600b001a29183a49cmr6998070plk.32.1683473531065; Sun, 07 May 2023 08:32:11 -0700 (PDT) Received: from [10.4.245.5] ([139.177.225.232]) by smtp.gmail.com with ESMTPSA id e9-20020a17090301c900b001ac7af57fd4sm120008plh.86.2023.05.07.08.32.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 07 May 2023 08:32:10 -0700 (PDT) Message-ID: <9b3abfd1-e925-61fe-80c0-6076b03f49f9@bytedance.com> Date: Sun, 7 May 2023 23:32:05 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [External] Re: [PATCH v2] blk-throttle: Fix io statistics for cgroup v1 To: Andrea Righi Cc: tj@kernel.org, josef@toxicpanda.com, axboe@kernel.dk, cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <20230401094708.77631-1-hanjinke.666@bytedance.com> <6696100e-e838-d96a-2894-bbca9783d2a3@bytedance.com> From: hanjinke In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 在 2023/5/6 下午7:44, Andrea Righi 写道: > On Fri, May 05, 2023 at 09:35:21PM +0800, hanjinke wrote: >> >> >> 在 2023/5/5 上午5:13, Andrea Righi 写道: >>> On Thu, May 04, 2023 at 11:08:53PM +0800, hanjinke wrote: >>>> Hi >>>> >>>> Sorry for delay（Chinese Labor Day holiday). >>> >>> No problem, it was also Labor Day in Italy. :) >>> >>>> >>>> 在 2023/4/29 上午3:05, Andrea Righi 写道: >>>>> On Sat, Apr 01, 2023 at 05:47:08PM +0800, Jinke Han wrote: >>>>>> From: Jinke Han >>>>>> >>>>>> After commit f382fb0bcef4 ("block: remove legacy IO schedulers"), >>>>>> blkio.throttle.io_serviced and blkio.throttle.io_service_bytes become >>>>>> the only stable io stats interface of cgroup v1, and these statistics >>>>>> are done in the blk-throttle code. But the current code only counts the >>>>>> bios that are actually throttled. When the user does not add the throttle >>>>>> limit, the io stats for cgroup v1 has nothing. I fix it according to the >>>>>> statistical method of v2, and made it count all ios accurately. >>>>>> >>>>>> Fixes: a7b36ee6ba29 ("block: move blk-throtl fast path inline") >>>>>> Signed-off-by: Jinke Han >>>>> >>>>> Thanks for fixing this! >>>>> >>>>> The code looks correct to me, but this seems to report io statistics >>>>> only if at least one throttling limit is defined. IIRC with cgroup v1 it >>>>> was possible to see the io statistics inside a cgroup also with no >>>>> throttling limits configured. >>>>> >>>>> Basically to restore the old behavior we would need to drop the >>>>> cgroup_subsys_on_dfl() check, something like the following (on top of >>>>> your patch). >>>>> >>>>> But I'm not sure if we're breaking other behaviors in this way... >>>>> opinions? >>>>> >>>>> block/blk-cgroup.c | 3 --- >>>>> block/blk-throttle.h | 12 +++++------- >>>>> 2 files changed, 5 insertions(+), 10 deletions(-) >>>>> >>>>> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c >>>>> index 79138bfc6001..43af86db7cf3 100644 >>>>> --- a/block/blk-cgroup.c >>>>> +++ b/block/blk-cgroup.c >>>>> @@ -2045,9 +2045,6 @@ void blk_cgroup_bio_start(struct bio *bio) >>>>> struct blkg_iostat_set *bis; >>>>> unsigned long flags; >>>>> - if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) >>>>> - return; >>>>> - >>>>> /* Root-level stats are sourced from system-wide IO stats */ >>>>> if (!cgroup_parent(blkcg->css.cgroup)) >>>>> return; >>>>> diff --git a/block/blk-throttle.h b/block/blk-throttle.h >>>>> index d1ccbfe9f797..bcb40ee2eeba 100644 >>>>> --- a/block/blk-throttle.h >>>>> +++ b/block/blk-throttle.h >>>>> @@ -185,14 +185,12 @@ static inline bool blk_should_throtl(struct bio *bio) >>>>> struct throtl_grp *tg = blkg_to_tg(bio->bi_blkg); >>>>> int rw = bio_data_dir(bio); >>>>> - if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) { >>>>> - if (!bio_flagged(bio, BIO_CGROUP_ACCT)) { >>>>> - bio_set_flag(bio, BIO_CGROUP_ACCT); >>>>> - blkg_rwstat_add(&tg->stat_bytes, bio->bi_opf, >>>>> - bio->bi_iter.bi_size); >>>>> - } >>>>> - blkg_rwstat_add(&tg->stat_ios, bio->bi_opf, 1); >>>>> + if (!bio_flagged(bio, BIO_CGROUP_ACCT)) { >>>>> + bio_set_flag(bio, BIO_CGROUP_ACCT); >>>>> + blkg_rwstat_add(&tg->stat_bytes, bio->bi_opf, >>>>> + bio->bi_iter.bi_size); >>>>> } >>>>> + blkg_rwstat_add(&tg->stat_ios, bio->bi_opf, 1); >>>> >> >> I checked the code again. If we remove cgroup_subsys_on_dfl check here, io >> statistics will still be performed in the case of v2, which I think is >> unnecessary, and this information will be counted to >> io_service_bytes/io_serviced, these two files are not visible in v2. Am I >> missing something? > > You are absolutely right. Sorry, I have just re-tested your fix and it > seems to handle the cgroup v1 case correctly, you can add my: > > Tested-by: Andrea Righi > > And we definitely need the cgroup_subsys_on_dfl() check, otherwise we'd > account extra IO in the v2 case that is not really needed. > Thanks a lot! I will add it and send a v3. Thanks， Jinke