linux-kernel - [PATCH v2 5/5] fs: new_inode_single() and iput

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Date:	Sat, 29 Nov 2008 09:45:09 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Ingo Molnar <mingo@...e.hu>, Christoph Hellwig <hch@...radead.org>
CC:	David Miller <davem@...emloft.net>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
	"kernel-testers@...r.kernel.org >> Kernel Testers List" 
	<kernel-testers@...r.kernel.org>, Mike Galbraith <efault@....de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, Al Viro <viro@...IV.linux.org.uk>
Subject: [PATCH v2 5/5] fs: new_inode_single() and iput_single()

Goal of this patch is to not touch inode_lock for socket/pipes/anonfd
inodes allocation/freeing.

SINGLE dentries are attached to inodes that dont need to be linked
in a list of inodes, being "inode_in_use" or "sb->s_inodes"
As inode_lock was taken only to protect these lists, we avoid 
taking it as well.

Using iput_single() from dput_single() 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()

(socket8 bench result : from 19.9s to 2.3s)

Signed-off-by: Eric Dumazet <dada1@...mosbay.com>
---
 fs/anon_inodes.c   |    2 +-
 fs/dcache.c        |    2 +-
 fs/inode.c         |   29 ++++++++++++++++++++---------
 fs/pipe.c          |    2 +-
 include/linux/fs.h |   12 +++++++++++-
 net/socket.c       |    2 +-
 6 files changed, 35 insertions(+), 14 deletions(-)

View attachment "new_inode_single.patch" of type "text/plain" (4081 bytes)