From: Jan Kara <jack@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 01/11] quota: Improve locking
Date: Mon, 26 Jan 2009 11:04:27 +0100 [thread overview]
Message-ID: <20090126100427.GA2726@duck.suse.cz> (raw)
In-Reply-To: <20090123234912.f78d75a0.akpm@linux-foundation.org>
On Fri 23-01-09 23:49:12, Andrew Morton wrote:
> On Fri, 16 Jan 2009 19:08:09 +0100 Jan Kara <jack@suse.cz> wrote:
>
> > static DEFINE_SPINLOCK(dq_list_lock);
> > +static DEFINE_SPINLOCK(dq_state_lock);
> > DEFINE_SPINLOCK(dq_data_lock);
>
> The chances are very good that two or even three of these locks will
> all get placed into the same cacheline in main memory. The effects
> will be quite bad if different CPUs (or, worse, different nodes) are
> taking these locks.
>
> For single, kernel-wide locks like these I think we should almost
> always pad out to a cacheline.
I never thought about this. Thanks for the idea.
> With __cacheline_aligned_in_smp, rather than __cacheline_aligned.
> Because spinlocks do take space even in uniprocessor builds.
I've added this to my list of quota cleanups.
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
prev parent reply other threads:[~2009-01-26 10:04 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <yes>
2009-01-16 18:08 ` Quota fixes and improvements Jan Kara
2009-01-16 18:08 ` [PATCH 01/11] quota: Improve locking Jan Kara
2009-01-16 18:08 ` [PATCH 02/11] ocfs2: Remove ocfs2_dquot_initialize() and ocfs2_dquot_drop() Jan Kara
2009-01-16 18:08 ` [PATCH 03/11] ocfs2: Push out dropping of dentry lock to ocfs2_wq Jan Kara
2009-01-16 18:08 ` [PATCH 04/11] ocfs2: Fix possible deadlock in ocfs2_write_dquot() Jan Kara
2009-01-16 18:08 ` [PATCH 05/11] quota: Add quota reservation support Jan Kara
2009-01-16 18:08 ` [PATCH 06/11] quota: Add quota reservation claim and released operations Jan Kara
2009-01-16 18:08 ` [PATCH 07/11] quota: Use inode->i_blkbits to get block bits Jan Kara
2009-01-16 18:08 ` [PATCH 08/11] quota: Move EXPORT_SYMBOL immediately next to the functions/varibles Jan Kara
2009-01-16 18:08 ` [PATCH 09/11] ext3: Remove unnecessary quota functions Jan Kara
2009-01-16 18:08 ` [PATCH 10/11] ext4: " Jan Kara
2009-01-16 18:08 ` [PATCH 11/11] reiserfs: " Jan Kara
2009-01-20 21:41 ` [PATCH 10/11] ext4: " Mingming Cao
2009-01-20 21:41 ` [PATCH 09/11] ext3: " Mingming Cao
2009-01-24 7:49 ` [PATCH 01/11] quota: Improve locking Andrew Morton
2009-01-26 10:04 ` Jan Kara [this message]
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