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From: Vivek Goyal <vgoyal@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org,
	ctalbott@google.com, rni@google.com
Subject: Re: [PATCHSET] block: remove ioc_*_changed()
Date: Tue, 20 Mar 2012 11:51:18 -0400	[thread overview]
Message-ID: <20120320155118.GC17071@redhat.com> (raw)
In-Reply-To: <1332195059-2750-1-git-send-email-tj@kernel.org>

On Mon, Mar 19, 2012 at 03:10:55PM -0700, Tejun Heo wrote:
> Hello, guys.
> 
> The changed notification used by cfq is rather odd.  cfq caches the
> associated cfqqs per cic and uses the changed notification to expire
> those lookup caches.
> 
> The explicit notification mechanism might make sense if determining
> whether the current cache is up-to-date is difficult or expensive;
> however, that isn't the case here.  Determining whether ioprio or
> cgroup has changed is straight-forward and inexpensive.
> 
> This patchset updates cfq to so that it remembers the current ioprio
> and blkcg in the cic and determines whether cfqq's need to be reset
> without using the changed notification and drops the changed
> notification code.

Hi Tejun,

So this patch still breaks cic->cfqq association in asynchronous
manner, when new request comes in. So it will still not solve the
problem I reported where after doing IO a task changes cgroup and
tries to delete the old cgroup and hangs forever as cic->cfqq is still
holding a reference to cgroup?

Thanks
Vivek

  parent reply	other threads:[~2012-03-20 15:51 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-03-19 22:10 [PATCHSET] block: remove ioc_*_changed() Tejun Heo
2012-03-19 22:10 ` [PATCH 1/4] blkcg: add blkcg->id Tejun Heo
2012-03-19 22:10 ` [PATCH 2/4] cfq: pass around cfq_io_cq instead of io_context Tejun Heo
2012-03-19 22:10 ` [PATCH 3/4] cfq: don't use icq_get_changed() Tejun Heo
2012-03-19 22:10 ` [PATCH 4/4] block: remove ioc_*_changed() Tejun Heo
2012-03-20 11:49 ` [PATCHSET] " Jens Axboe
2012-03-20 15:51 ` Vivek Goyal [this message]
2012-03-20 15:53   ` Tejun Heo
2012-03-20 16:00     ` Vivek Goyal

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