From: Tejun Heo <tj@kernel.org>
To: Kent Overstreet <koverstreet@google.com>
Cc: axboe@kernel.dk, vgoyal@redhat.com, ctalbott@google.com,
rni@google.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 7/9] block: implement bio_associate_current()
Date: Fri, 17 Feb 2012 14:14:06 -0800 [thread overview]
Message-ID: <20120217221406.GJ29414@google.com> (raw)
In-Reply-To: <20120217011907.GA15073@google.com>
Hello, Kent.
On Thu, Feb 16, 2012 at 05:19:07PM -0800, Kent Overstreet wrote:
> On Thu, Feb 16, 2012 at 02:37:56PM -0800, Tejun Heo wrote:
> > This patch implements bio_associate_current() which associates the
> > specified bio with %current. The bio will record the associated ioc
> > and blkcg at that point and block layer will use the recorded ones
> > regardless of which task actually ends up issuing the bio. bio
> > release puts the associated ioc and blkcg.
>
> Excellent.
>
> Why not have bio_associate_current() called from submit_bio()? I would
> expect that's what we want most of the time, and the places it's not
> (mainly writeback) calling it before submit_bio() would do the right
> thing.
>
> It'd make things more consistent - rq_ioc() could be dropped, and
> incorrect usage would be more obvious.
Yeah, maybe, I was mostly trying to avoid adding extra operations on
common paths as explicit task association isn't that common, at least
for now. That said, I agree that things can be much cleaner just
allocating and associating stuff upfront - ie. always have ioc and
associate blkcg with IOs on issue.
If the associated blkcg is used consistently through block layer, it
might be better but cfq doesn't even do that. It has its own icq ->
blkcg mapping, which it initializes on first cfqq association. It
even ignores tasks migrating to a different cgroup and keeps using
whatever cgroup the task first issued IOs on. :(
I don't know. Maybe someday.
Thanks.
--
tejun
next prev parent reply other threads:[~2012-02-17 22:14 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-16 22:37 [PATCHSET] blkcg: update locking and fix stacking Tejun Heo
2012-02-16 22:37 ` [PATCH 1/9] blkcg: use double locking instead of RCU for blkg synchronization Tejun Heo
2012-02-16 22:37 ` [PATCH 2/9] blkcg: drop unnecessary RCU locking Tejun Heo
2012-02-17 16:19 ` Vivek Goyal
2012-02-17 17:07 ` Tejun Heo
2012-02-17 17:14 ` Tejun Heo
2012-02-17 16:47 ` Vivek Goyal
2012-02-17 17:11 ` Tejun Heo
2012-02-17 17:28 ` Vivek Goyal
2012-02-17 17:43 ` Tejun Heo
2012-02-17 18:08 ` Vivek Goyal
2012-02-17 18:16 ` Tejun Heo
2012-02-22 0:49 ` [PATCH UPDATED " Tejun Heo
2012-02-16 22:37 ` [PATCH 3/9] block: restructure get_request() Tejun Heo
2012-02-16 22:37 ` [PATCH 4/9] block: interface update for ioc/icq creation functions Tejun Heo
2012-02-16 22:37 ` [PATCH 5/9] block: ioc_task_link() can't fail Tejun Heo
2012-02-17 20:41 ` Vivek Goyal
2012-02-17 22:18 ` Tejun Heo
2012-02-16 22:37 ` [PATCH 6/9] block: add io_context->active_ref Tejun Heo
2012-02-16 22:37 ` [PATCH 7/9] block: implement bio_associate_current() Tejun Heo
2012-02-17 1:19 ` Kent Overstreet
2012-02-17 22:14 ` Tejun Heo [this message]
2012-02-17 22:34 ` Vivek Goyal
2012-02-17 22:41 ` Tejun Heo
2012-02-17 22:51 ` Vivek Goyal
2012-02-17 22:57 ` Tejun Heo
2012-02-20 14:22 ` Vivek Goyal
2012-02-20 16:59 ` Tejun Heo
2012-02-20 19:14 ` Vivek Goyal
2012-02-20 21:21 ` Tejun Heo
2012-02-27 23:12 ` Chris Wright
2012-02-28 14:10 ` Vivek Goyal
2012-02-28 17:01 ` Chris Wright
2012-02-28 20:11 ` Stefan Hajnoczi
2012-02-20 14:36 ` Vivek Goyal
2012-02-20 17:01 ` Tejun Heo
2012-02-20 19:16 ` Vivek Goyal
2012-02-20 21:06 ` Tejun Heo
2012-02-20 21:10 ` Vivek Goyal
2012-02-17 22:56 ` Vivek Goyal
2012-02-17 23:06 ` Tejun Heo
2012-02-17 21:33 ` Vivek Goyal
2012-02-17 22:03 ` Tejun Heo
2012-02-17 22:29 ` Vivek Goyal
2012-02-17 22:38 ` Tejun Heo
2012-02-17 22:42 ` Tejun Heo
2012-02-16 22:37 ` [PATCH 8/9] block: make block cgroup policies follow bio task association Tejun Heo
2012-02-16 22:37 ` [PATCH 9/9] block: make blk-throttle preserve the issuing task on delayed bios Tejun Heo
2012-02-17 21:58 ` Vivek Goyal
2012-02-17 22:17 ` Tejun Heo
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