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From: Tejun Heo <tj@kernel.org>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: axboe@kernel.dk, newella@fb.com, clm@fb.com,
	josef@toxicpanda.com, dennisz@fb.com, lizefan@huawei.com,
	hannes@cmpxchg.org, linux-kernel@vger.kernel.org,
	linux-block@vger.kernel.org, kernel-team@fb.com,
	cgroups@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
	kafai@fb.com, songliubraving@fb.com, yhs@fb.com,
	bpf@vger.kernel.org, Josef Bacik <jbacik@fb.com>
Subject: Re: [PATCH 08/10] blkcg: implement blk-ioweight
Date: Sat, 15 Jun 2019 08:57:43 -0700
Message-ID: <20190615155743.GF657710@devbig004.ftw2.facebook.com> (raw)
In-Reply-To: <87blyzc2n9.fsf@toke.dk>

Hello,

On Fri, Jun 14, 2019 at 10:50:34PM +0200, Toke Høiland-Jørgensen wrote:
> > Within a single cgroup, the IOs are FIFO. When an IO has enough vtime
> > credit, it just passes through. When it doesn't, it always waits
> > behind any other IOs which are already waiting.
> 
> OK. Is there any fundamental reason why requests from individual
> processes could not be interleaved? Or does it just not give the same
> benefits in an IO request context as it does for network packets?

I don't think there's any fundamental reason we can't.  Currently, it
just isn't doing anything it doesn't have to do while preserving the
existing ordering.  One different from networking could be that
there's more sharing - buffered writes are attributed to the whole
domain (either system or cgroup) rather than individual tasks, so the
ownership of IOs gets a bit mushy beyond resource domain level.

Thanks.

-- 
tejun

  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-14  1:56 [PATCHSET block/for-next] IO cost model based work-conserving porportional controller Tejun Heo
2019-06-14  1:56 ` [PATCH 01/10] blkcg: pass @q and @blkcg into blkcg_pol_alloc_pd_fn() Tejun Heo
2019-06-14  1:56 ` [PATCH 02/10] blkcg: make ->cpd_init_fn() optional Tejun Heo
2019-06-14  1:56 ` [PATCH 03/10] blkcg: separate blkcg_conf_get_disk() out of blkg_conf_prep() Tejun Heo
2019-06-14  1:56 ` [PATCH 04/10] block/rq_qos: add rq_qos_merge() Tejun Heo
2019-06-14  1:56 ` [PATCH 05/10] block/rq_qos: implement rq_qos_ops->queue_depth_changed() Tejun Heo
2019-06-14  1:56 ` [PATCH 06/10] blkcg: s/RQ_QOS_CGROUP/RQ_QOS_LATENCY/ Tejun Heo
2019-06-14  1:56 ` [PATCH 07/10] blk-mq: add optional request->pre_start_time_ns Tejun Heo
2019-06-14  1:56 ` [PATCH 08/10] blkcg: implement blk-ioweight Tejun Heo
2019-06-14 12:17   ` Toke Høiland-Jørgensen
2019-06-14 15:09     ` Tejun Heo
2019-06-14 20:50       ` Toke Høiland-Jørgensen
2019-06-15 15:57         ` Tejun Heo [this message]
2019-06-14  1:56 ` [PATCH 09/10] blkcg: add tools/cgroup/monitor_ioweight.py Tejun Heo
2019-06-14  1:56 ` [PATCH 10/10] blkcg: implement BPF_PROG_TYPE_IO_COST Tejun Heo
2019-06-14 11:32   ` Quentin Monnet
2019-06-14 14:52     ` Tejun Heo
2019-06-14 16:35       ` Alexei Starovoitov
2019-06-14 17:09         ` Tejun Heo
2019-06-14 17:56 ` [PATCHSET block/for-next] IO cost model based work-conserving porportional controller Tejun Heo

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