From: Christoph Hellwig <hch@lst.de>
To: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Chris Mason <clm@meta.com>,
Josef Bacik <josef@toxicpanda.com>, Chris Mason <clm@fb.com>,
David Sterba <dsterba@suse.com>, Jens Axboe <axboe@kernel.dk>,
cgroups@vger.kernel.org, linux-block@vger.kernel.org,
linux-btrfs@vger.kernel.org
Subject: Re: move bio cgroup punting into btrfs
Date: Thu, 30 Mar 2023 02:15:52 +0200 [thread overview]
Message-ID: <20230330001552.GA2381@lst.de> (raw)
In-Reply-To: <ZCSOgoe84BhiUZcn@slm.duckdns.org>
On Wed, Mar 29, 2023 at 09:16:18AM -1000, Tejun Heo wrote:
> We didn't really look deep into adding the support but Chris mentioned that
> raid5/6 are likely to need something similar. Maybe this is because my grasp
> of filesytsems is pretty weak but the pattern doesn't seem unreasonable to
> me. There's some work to be done by a shread kthread and that sometimes can
> fork out IOs which belong to specific cgroups.
Well, in a cgroup aware writeback path we'd always be off much better
to just do the work from a cgroup specific thread instead of bouncing
it around.
> At least in the IO control and direct issue path, punting to just one thread
> hasn't been a practical problem given that when the issuing thread needs to
> be blocked, either the whole device or the cgroup needs to be throttled
> anyway.
I don't think it is a problem per see. But it is: a) inefficient and
b) complex in terms of code. So why bounce around between 2, or in case
of writeback 3 threads for a single I/O, instead of making sure your
offload threads are simplify cgroup specific to start with?
prev parent reply other threads:[~2023-03-30 0:15 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-27 0:49 move bio cgroup punting into btrfs Christoph Hellwig
2023-03-27 0:49 ` Christoph Hellwig
[not found] ` <20230327004954.728797-1-hch-jcswGhMUV9g@public.gmane.org>
2023-03-27 0:49 ` [PATCH 1/7] btrfs: move kthread_associate_blkcg out of btrfs_submit_compressed_write Christoph Hellwig
2023-03-27 0:49 ` Christoph Hellwig
2023-03-27 0:49 ` [PATCH 2/7] btrfs: don't free the async_extent in submit_uncompressed_range Christoph Hellwig
2023-03-27 0:49 ` Christoph Hellwig
2023-03-27 0:49 ` [PATCH 5/7] btrfs, block: move REQ_CGROUP_PUNT to btrfs Christoph Hellwig
2023-03-27 0:49 ` Christoph Hellwig
2023-03-28 1:15 ` Jens Axboe
2023-03-27 0:49 ` [PATCH 7/7] block: make blkcg_punt_bio_submit optional Christoph Hellwig
2023-03-27 0:49 ` Christoph Hellwig
2023-03-27 23:32 ` Jens Axboe
2023-03-27 23:32 ` Jens Axboe
2023-03-27 0:49 ` [PATCH 3/7] btrfs: also use kthread_associate_blkcg for uncompressible ranges Christoph Hellwig
2023-03-27 0:49 ` [PATCH 4/7] btrfs, mm: remove the punt_to_cgroup field in struct writeback_control Christoph Hellwig
2023-03-27 0:49 ` [PATCH 6/7] block: async_bio_lock does not need to be bh-safe Christoph Hellwig
2023-03-27 23:31 ` Jens Axboe
2023-03-27 23:31 ` Jens Axboe
2023-03-27 23:18 ` move bio cgroup punting into btrfs David Sterba
[not found] ` <20230327231837.GK10580-1ReQVI26iDCaZKY3DrU6dA@public.gmane.org>
2023-03-31 17:25 ` David Sterba
2023-03-31 17:25 ` David Sterba
2023-03-28 21:18 ` Chris Mason
[not found] ` <512eaacf-3ff6-f4f9-c856-a0e03c027501-M8Ki61LpUEw@public.gmane.org>
2023-03-28 23:34 ` Christoph Hellwig
2023-03-28 23:34 ` Christoph Hellwig
2023-03-29 19:16 ` Tejun Heo
2023-03-30 0:15 ` Christoph Hellwig [this message]
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