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From: Vivek Goyal <vgoyal@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: axboe@kernel.dk, akpm@linux-foundation.org,
	linux-kernel@vger.kernel.org, dpshah@google.com,
	ctalbott@google.com, rni@google.com
Subject: Re: [PATCH 5/5] blkcg: remove blkio_group->stats_lock
Date: Fri, 9 Mar 2012 12:15:23 -0500	[thread overview]
Message-ID: <20120309171523.GB7746@redhat.com> (raw)
In-Reply-To: <1331232840-16044-6-git-send-email-tj@kernel.org>

On Thu, Mar 08, 2012 at 10:54:00AM -0800, Tejun Heo wrote:
> With recent plug merge updates, all non-percpu stat updates happen
> under queue_lock making stats_lock unnecessary to synchronize stat
> updates.  The only synchronization necessary is stat reading, which
> can be done using u64_stats_sync instead.
> 
> This patch removes blkio_group->stats_lock and adds
> blkio_group_stats->syncp for reader synchronization.
> 

Good to see stat_lock going away. That lock was confusing as we were doing
updates under queue_lock anyway. One less lock to think about now.

This stat code is messy though. All time related stat, maintaining flags,
dividing stats between read/write, sync/async. I think we are maintaining
way too much of stat. (/me wished there was a way to get rid of some of
the stats and make code simpler).

Thanks
Vivek

  reply	other threads:[~2012-03-09 17:56 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-03-08 18:53 [PATCHSET] blkcg: fix percpu stat allocation and remove stats_lock, take#2 Tejun Heo
2012-03-08 18:53 ` [PATCH 1/5] blkcg: alloc per cpu stats from worker thread in a delayed manner Tejun Heo
2012-03-08 18:53 ` [PATCH 2/5] blkcg: don't use percpu for merged stats Tejun Heo
2012-03-08 18:53 ` [PATCH 3/5] blkcg: simplify stat reset Tejun Heo
2012-03-08 18:53 ` [PATCH 4/5] blkcg: restructure blkio_get_stat() Tejun Heo
2012-03-08 18:54 ` [PATCH 5/5] blkcg: remove blkio_group->stats_lock Tejun Heo
2012-03-09 17:15   ` Vivek Goyal [this message]
2012-03-09 18:03     ` Tejun Heo

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