From: Vivek Goyal <vgoyal@redhat.com>
To: linux-kernel@vger.kernel.org, jaxboe@fusionio.com, axboe@kernel.dk
Cc: dpshah@google.com
Subject: Re: [PATCH 00/13] blk-throttle: lockless bio processing for no throttle rule group [V2]
Date: Thu, 19 May 2011 15:58:59 -0400 [thread overview]
Message-ID: <20110519195859.GF12600@redhat.com> (raw)
In-Reply-To: <1305833911-7717-1-git-send-email-vgoyal@redhat.com>
On Thu, May 19, 2011 at 03:38:18PM -0400, Vivek Goyal wrote:
> Hi,
>
> This is V2 of the patch. Changes from V1 are.
>
> - Dropped first patch of the series which has already been merged.
> - Fixed couple of white space warnings.
>
> Jens, I am sending this series on your both the ids. See if both produce
> warnings.
>
> Block throttling code takes request queue lock for every incoming bio
> (blk_throtl_bio()). This is true even if there are no throttle rules in
> the group. This is a common case for root cgroup where distributions
> will have throttling support compiled in but a vast majority of users
> will not be specifying throttling rule.
>
> This patch series tries to make bio processing lockless (no requeust
> queue lock), if there are no rules specified for the group. Once
> a bio is submitted, under rcu_read_lock() we search for the group,
> update the stats and release the rcu lock. request queue lock is taken
> only if there are throttling rules specified in the group.
>
> I have made some of the dispatch stats per cpu so that these can be updated
> without taking request queue lock.
Also forgot to mention that now throttling path does not take blkg->stat_lock
at all. Throttling updates only 3 stats and all these 3 stats have been
converted to per cpu, hence we got rid of the need of taking blkg->stat_lock
also.
Divyesh, can you have a look at locking changes around stats and see if
you have any concerns.
Thanks
Vivek
prev parent reply other threads:[~2011-05-19 19:59 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-19 19:38 [PATCH 00/13] blk-throttle: lockless bio processing for no throttle rule group [V2] Vivek Goyal
2011-05-19 19:38 ` [PATCH 01/13] blk-throttle: Do the new group initialization with the help of a function Vivek Goyal
2011-05-19 19:38 ` [PATCH 02/13] blk-cgroup: move some fields of unaccounted_time file under right config option Vivek Goyal
2011-05-19 19:38 ` [PATCH 03/13] cfq-iosched: Get rid of redundant function parameter "create" Vivek Goyal
2011-05-19 19:38 ` [PATCH 04/13] cfq-iosched: Fix a possible race with cfq cgroup removal code Vivek Goyal
2011-05-19 19:38 ` [PATCH 05/13] blk-cgroup: Allow sleeping while dynamically allocating a group Vivek Goyal
2011-05-19 19:38 ` [PATCH 06/13] blk-throttle: Dynamically allocate root group Vivek Goyal
2011-05-19 19:38 ` [PATCH 07/13] blk-throttle: Introduce a helper function to fill in device details Vivek Goyal
2011-05-19 19:38 ` [PATCH 08/13] blk-throttle: Use helper function to add root throtl group to lists Vivek Goyal
2011-05-19 19:38 ` [PATCH 09/13] blk-throttle: Free up a group only after one rcu grace period Vivek Goyal
2011-05-19 19:38 ` [PATCH 10/13] blk-throttle: Make dispatch stats per cpu Vivek Goyal
2011-05-19 19:38 ` [PATCH 11/13] blk-cgroup: Make 64bit per cpu stats safe on 32bit arch Vivek Goyal
2011-05-19 19:38 ` [PATCH 12/13] blk-cgroup: Make cgroup stat reset path blkg->lock free for dispatch stats Vivek Goyal
2011-05-19 19:38 ` [PATCH 13/13] blk-throttle: Make no throttling rule group processing lockless Vivek Goyal
2011-05-19 19:58 ` Vivek Goyal [this message]
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