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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 CCF22C4320A for ; Sat, 24 Jul 2021 07:12:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A429260EB1 for ; Sat, 24 Jul 2021 07:12:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234142AbhGXGcN (ORCPT ); Sat, 24 Jul 2021 02:32:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33020 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229884AbhGXGcM (ORCPT ); Sat, 24 Jul 2021 02:32:12 -0400 Received: from mail-wr1-x431.google.com (mail-wr1-x431.google.com [IPv6:2a00:1450:4864:20::431]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42416C061575 for ; Sat, 24 Jul 2021 00:12:44 -0700 (PDT) Received: by mail-wr1-x431.google.com with SMTP id r2so4692363wrl.1 for ; Sat, 24 Jul 2021 00:12:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=k3SIdqJjNcyvIqzg9OTyrS4+nLskMR74WbnTGXaM2FI=; b=QJwk/7TiSiakAcpE9Vec9Cx0F3PgBamBMd79JFBz9jEb2ATPlLYk4ASZKHBwFafnuC kvcxc0VS4ar1tM7Wb4Bq+WQgwNz6zR9svs1CQ213K5oA+mYoaO1eoNl+PwVZ49eas8Gm 4bEV9mBBxJxAY6ZOM3fMwSHvvQbSsEbFDcKijOBRa5swvgtiGwt22a8rJt1Q0MSp3QLl UWXmnj7o3d4wA4LRgR81FMQJ2ut5qXoueUmFP+vowUBlXEGShUgdskzkO9QoqbP1XGMr Won1phpvM/4fjVZdfpICB/VI4386dHy02o6piPRl0cdNWIanBCapmCPtHQl0tgCSdLy9 SIBg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=k3SIdqJjNcyvIqzg9OTyrS4+nLskMR74WbnTGXaM2FI=; b=f01GTajCqsq22P+cugNbNLrgBWAfyPqXVqc1fWiaCViHtKhh9T3vu33/fsXuvVEFS6 ZLicztIygLylUbzD04WU3X8UkEdZH112p4Mo8Qqsppdor/+CI7mfXI3Pzz43z/wwxBJ6 LGd7WqHsMVDjYNUzR5sruSPMw5pBlLcK5UcrYr0D6gyW4Ge/CQe8pm2xedU5aVwMqiBY gme5ZSOaae3RaBa/ktmQHlaQtmsfxt9hR/w8QjLTK/3WudAOYREvzQ6DbA6mBNBa41jr wk13eRwvvT+foH/DbdMEelIvAitP7qz68fd2pPMIV6P/1yx/4eFLipG8R9ijfYtcaWz9 2z7g== X-Gm-Message-State: AOAM532Xt9SjDmDcXkarb4M07zVv8FwroCS8ntEoS0K+iHKToWdw5ge8 pAq4qhylexo3Y3Hm90CFMjbw2w== X-Google-Smtp-Source: ABdhPJwXK5nPxvdGlT/rVSBS+XRXgw/Wbg46XiAXHkMQQdMy79INIKuWmEAaxaLICAQ/76yv57rYxg== X-Received: by 2002:a05:6000:1801:: with SMTP id m1mr3378865wrh.198.1627110762689; Sat, 24 Jul 2021 00:12:42 -0700 (PDT) Received: from [192.168.0.13] ([83.216.184.132]) by smtp.gmail.com with ESMTPSA id c15sm29316186wmr.28.2021.07.24.00.12.41 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 24 Jul 2021 00:12:42 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\)) Subject: Re: [PATCH 1/3] block, bfq: do not idle if only one cgroup is activated From: Paolo Valente In-Reply-To: <20210714094529.758808-2-yukuai3@huawei.com> Date: Sat, 24 Jul 2021 09:12:40 +0200 Cc: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com Content-Transfer-Encoding: quoted-printable Message-Id: <7DF40BD4-8F57-4C2E-88A9-CBC3DA2A891E@linaro.org> References: <20210714094529.758808-1-yukuai3@huawei.com> <20210714094529.758808-2-yukuai3@huawei.com> To: Yu Kuai X-Mailer: Apple Mail (2.3445.104.11) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Il giorno 14 lug 2021, alle ore 11:45, Yu Kuai ha = scritto: >=20 > If only one group is activated, specifically > 'bfqd->num_groups_with_pending_reqs =3D=3D 1', there is no need to = guarantee > the same share of the throughput of queues in the same group. >=20 > Thus change the condition from '> 0' to '> 1' in > bfq_asymmetric_scenario(). I see your point, and I agree with your goal. Yet, your change seems not to suffer from the following problem. In addition to the groups that are created explicitly, there is the implicit root group. So, when bfqd->num_groups_with_pending_reqs =3D=3D 1, there may be both active processes in the root group and active processes in the only group created explicitly. In this case, idling is needed to preserve service guarantees. Probably your idea should be improved by making sure that there is pending I/O only from either the root group or the explicit group. Thanks, Paolo > By the way, if 'num_groups_with_pending_reqs' > is greater than 1, there is no need to check 'varied_queue_weights' = and > 'multiple_classes_busy', thus move the judgement forward. >=20 > Test procedure: > run "fio -numjobs=3D1 -ioengine=3Dpsync -bs=3D4k -direct=3D1 = -rw=3Drandread..." multiple > times in the same cgroup(not root). >=20 > Test result: total bandwidth(Mib/s) > | total jobs | before this patch | after this patch | > | ---------- | ----------------- | --------------------- | > | 1 | 33.8 | 33.8 | > | 2 | 33.8 | 65.4 (32.7 each job) | > | 4 | 33.8 | 106.8 (26.7 each job) | > | 8 | 33.8 | 126.4 (15.8 each job) | >=20 > By the way, if I test with "fio -numjobs=3D1/2/4/8 ...", test result = is > the same with or without this patch. >=20 > Signed-off-by: Yu Kuai > --- > block/bfq-iosched.c | 25 ++++++++++++++++--------- > 1 file changed, 16 insertions(+), 9 deletions(-) >=20 > diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c > index 727955918563..2768a4c1cc45 100644 > --- a/block/bfq-iosched.c > +++ b/block/bfq-iosched.c > @@ -709,7 +709,9 @@ bfq_pos_tree_add_move(struct bfq_data *bfqd, = struct bfq_queue *bfqq) > * much easier to maintain the needed state: > * 1) all active queues have the same weight, > * 2) all active queues belong to the same I/O-priority class, > - * 3) there are no active groups. > + * 3) there is one active group at most. > + * If the last condition is false, there is no need to guarantee the > + * same share of the throughput of queues in the same group. > * In particular, the last condition is always true if hierarchical > * support or the cgroups interface are not enabled, thus no state > * needs to be maintained in this case. > @@ -717,7 +719,16 @@ bfq_pos_tree_add_move(struct bfq_data *bfqd, = struct bfq_queue *bfqq) > static bool bfq_asymmetric_scenario(struct bfq_data *bfqd, > struct bfq_queue *bfqq) > { > - bool smallest_weight =3D bfqq && > + bool smallest_weight; > + bool varied_queue_weights; > + bool multiple_classes_busy; > + > +#ifdef CONFIG_BFQ_GROUP_IOSCHED > + if (bfqd->num_groups_with_pending_reqs > 1) > + return true; > +#endif > + > + smallest_weight =3D bfqq && > bfqq->weight_counter && > bfqq->weight_counter =3D=3D > container_of( > @@ -729,21 +740,17 @@ static bool bfq_asymmetric_scenario(struct = bfq_data *bfqd, > * For queue weights to differ, queue_weights_tree must contain > * at least two nodes. > */ > - bool varied_queue_weights =3D !smallest_weight && > + varied_queue_weights =3D !smallest_weight && > !RB_EMPTY_ROOT(&bfqd->queue_weights_tree.rb_root) && > (bfqd->queue_weights_tree.rb_root.rb_node->rb_left || > bfqd->queue_weights_tree.rb_root.rb_node->rb_right); >=20 > - bool multiple_classes_busy =3D > + multiple_classes_busy =3D > (bfqd->busy_queues[0] && bfqd->busy_queues[1]) || > (bfqd->busy_queues[0] && bfqd->busy_queues[2]) || > (bfqd->busy_queues[1] && bfqd->busy_queues[2]); >=20 > - return varied_queue_weights || multiple_classes_busy > -#ifdef CONFIG_BFQ_GROUP_IOSCHED > - || bfqd->num_groups_with_pending_reqs > 0 > -#endif > - ; > + return varied_queue_weights || multiple_classes_busy; > } >=20 > /* > --=20 > 2.31.1 >=20