linux-kernel - Re: [PATCH RFC 0/2] Lockless update of reference count protected by spinlock

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Message-ID: <51C87477.9020505@hp.com>
Date:	Mon, 24 Jun 2013 12:31:51 -0400
From:	Waiman Long <waiman.long@...com>
To:	Waiman Long <Waiman.Long@...com>
CC:	Alexander Viro <viro@...iv.linux.org.uk>,
	Jeff Layton <jlayton@...hat.com>,
	Miklos Szeredi <mszeredi@...e.cz>,
	Ingo Molnar <mingo@...hat.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>
Subject: Re: [PATCH RFC 0/2] Lockless update of reference count protected
 by spinlock

On 06/19/2013 12:50 PM, Waiman Long wrote:
> This patchset supports a generic mechanism to atomically update
> a reference count that is protected by a spinlock without actually
> acquiring the lock itself. If the update doesn't succeeed, the caller
> will have to acquire the lock and update the reference count in the
> the old way.  This will help in situation where there is a lot of
> spinlock contention because of frequent reference count update.
>
> The new mechanism was designed in such a way to easily retrofit
> into existing code with minimal changes. Both the spinlock and the
> reference count can be accessed in the same way as before.
>
> The d_lock and d_count fields of the struct dentry in dcache.h was
> modified to use the new mechanism. This serves as an example of how
> to convert existing spinlock and reference count combo to use the
> new way of locklessly updating the reference count.
>
> Signed-off-by: Waiman Long<Waiman.Long@...com>
>
> Waiman Long (2):
>    spinlock: New spinlock_refcount.h for lockless update of refcount
>    dcache: Locklessly update d_count whenever possible
>
>   fs/dcache.c                       |   14 +++-
>   include/linux/dcache.h            |   22 +++++-
>   include/linux/spinlock_refcount.h |  145 +++++++++++++++++++++++++++++++++++++
>   include/linux/spinlock_types.h    |   19 +++++
>   4 files changed, 196 insertions(+), 4 deletions(-)
>   create mode 100644 include/linux/spinlock_refcount.h
>

So far, I haven't received any feedback on this patch. I would really 
appreciate if someone could let me know if there is any improvement that 
will make this patch more merge-able.

Thanks,
Longman
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