linux-kernel - Re: [PATCH 5/6] fs: Introduce special inodes

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Message-Id: <20081127.002046.25550570.davem@davemloft.net>
Date:	Thu, 27 Nov 2008 00:20:46 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	dada1@...mosbay.com
Cc:	mingo@...e.hu, rjw@...k.pl, linux-kernel@...r.kernel.org,
	kernel-testers@...r.kernel.org, efault@....de,
	a.p.zijlstra@...llo.nl, netdev@...r.kernel.org,
	cl@...ux-foundation.org, hch@...radead.org
Subject: Re: [PATCH 5/6] fs: Introduce special inodes

From: Eric Dumazet <dada1@...mosbay.com>
Date: Thu, 27 Nov 2008 00:32:41 +0100

> Goal of this patch is to not touch inode_lock for socket/pipes/anonfd
>  inodes allocation/freeing.
> 
>  In new_inode(), we test if super block has MS_SPECIAL flag set.
>  If yes, we dont put inode in "inode_in_use" list nor "sb->s_inodes" list
>  As inode_lock was taken only to protect these lists, we avoid it as well
> 
>  Using iput_special() from dput_special() avoids taking inode_lock
>  at freeing time.
> 
>  This patch has a very noticeable effect, because we avoid dirtying of three contended cache lines in new_inode(), and five cache lines
>  in iput()
> 
> Note: Not sure if we can use MS_SPECIAL=MS_NOUSER, or if we
> really need a different flag.
> 
> (socket8 bench result : from 20.5s to 2.94s) 
> 
> Signed-off-by: Eric Dumazet <dada1@...mosbay.com>

No problem with networking part:

Acked-by: David S. Miller <davem@...emloft.net>
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