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From: Tejun Heo <tj@kernel.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, kernel-team@fb.com,
	linux-kernel@vger.kernel.org, Josef Bacik <josef@toxicpanda.com>
Subject: Re: [PATCH block-5.17] block: don't merge across cgroup boundaries if iocost or iolatency is active
Date: Mon, 14 Mar 2022 10:41:38 -1000	[thread overview]
Message-ID: <Yi+ogt9ahz3yr9RE@slm.duckdns.org> (raw)
In-Reply-To: <107965ce-a29a-b5f4-ef87-63b753380891@kernel.dk>

On Mon, Mar 14, 2022 at 02:12:34PM -0600, Jens Axboe wrote:
> > * Add WARN_ON_ONCE() on blkg mismatch in ioc_rqos_merge() so that we can
> >   easily notice similar failures in the future.
> > 
> > * Make sure iocost enable/disable transitions only happen when iocost is
> >   actually enabled / disabled.
> 
> Is there really no better way to do this than add a lot of expensive
> checks to the fast path?
> 
> Even just inverting the checks so that
> 
> if (req->bio->bi_blkg != bio->bi_blkg)
> 	...
> 
> is checked first would seem a lot saner.
> 
> In any case, since this isn't a new regression, I'd feel a lot better
> deferring it to 5.18.

As discussed, the only risk of removing the disable/enable switch and always
testing is ruining some merges for cases where blkcg is enabled but no
control is applied, which shouldn't be a big problem. I'll redo the patch.

Thanks.

-- 
tejun

  reply	other threads:[~2022-03-14 20:41 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-14  7:57 [PATCH block-5.17] block: don't merge across cgroup boundaries if iocost or iolatency is active Tejun Heo
2022-03-14 20:12 ` Jens Axboe
2022-03-14 20:41   ` Tejun Heo [this message]
2022-03-14 23:50 ` [PATCH v2 for-5.18/block] block: don't merge across cgroup boundaries if blkcg is enabled Tejun Heo
2022-03-15  0:30   ` [PATCH v3 " Tejun Heo
2022-03-15  1:15     ` Jens Axboe

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