From mboxrd@z Thu Jan 1 00:00:00 1970 From: "yukuai (C)" Subject: Re: [PATCH 2/4] block, bfq: avoid moving bfqq to it's parent bfqg Date: Tue, 21 Dec 2021 19:08:44 +0800 Message-ID: References: <20211221032135.878550-1-yukuai3@huawei.com> <20211221032135.878550-3-yukuai3@huawei.com> <20211221101659.GB24748@quack2.suse.cz> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20211221101659.GB24748@quack2.suse.cz> List-ID: Content-Type: text/plain; charset="iso-8859-1"; format="flowed" To: Jan Kara Cc: tj@kernel.org, axboe@kernel.dk, paolo.valente@linaro.org, fchecconi@gmail.com, avanzini.arianna@gmail.com, cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com =D4=DA 2021/12/21 18:16, Jan Kara =D0=B4=B5=C0: > On Tue 21-12-21 11:21:33, Yu Kuai wrote: >> Moving bfqq to it's parent bfqg is pointless. >> >> Signed-off-by: Yu Kuai >=20 > Did you notice that this is happening often enough that the check is worth > it? Where do we do this? >=20 I noticed that this will happend when root group is offlined: bfq_pd_offline bfq_put_async_queues __bfq_put_async_bfqq bfq_bfqq_move I'm not sure if there are other situations. I think bfq_bfqq_move() is not happening often itself, thus the checking won't affect performance. Thanks, Kuai > Honza >=20 >> --- >> block/bfq-cgroup.c | 7 ++++++- >> 1 file changed, 6 insertions(+), 1 deletion(-) >> >> diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c >> index 24a5c5329bcd..0f62546a72d4 100644 >> --- a/block/bfq-cgroup.c >> +++ b/block/bfq-cgroup.c >> @@ -645,6 +645,11 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bf= q_queue *bfqq, >> struct bfq_group *bfqg) >> { >> struct bfq_entity *entity =3D &bfqq->entity; >> + struct bfq_group *old_parent =3D bfq_group(bfqq); >> + >> + /* No point to move bfqq to the same group */ >> + if (old_parent =3D=3D bfqg) >> + return; >> =20 >> /* >> * Get extra reference to prevent bfqq from being freed in >> @@ -666,7 +671,7 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq= _queue *bfqq, >> bfq_deactivate_bfqq(bfqd, bfqq, false, false); >> else if (entity->on_st_or_in_serv) >> bfq_put_idle_entity(bfq_entity_service_tree(entity), entity); >> - bfqg_and_blkg_put(bfqq_group(bfqq)); >> + bfqg_and_blkg_put(old_parent); >> =20 >> if (entity->parent && >> entity->parent->last_bfqq_created =3D=3D bfqq) >> --=20 >> 2.31.1 >>