From: Andrew Morton <akpm@linux-foundation.org>
To: Jan Kara <jack@suse.cz>
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: Fri, 23 Jan 2009 23:49:12 -0800 [thread overview]
Message-ID: <20090123234912.f78d75a0.akpm@linux-foundation.org> (raw)
In-Reply-To: <1232129299-22018-2-git-send-email-jack@suse.cz>
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.
With __cacheline_aligned_in_smp, rather than __cacheline_aligned.
Because spinlocks do take space even in uniprocessor builds.
There are probably lots of existing locks which should be converted.
next prev parent reply other threads:[~2009-01-24 7:49 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 ` Andrew Morton [this message]
2009-01-26 10:04 ` [PATCH 01/11] quota: Improve locking Jan Kara
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