netdev - [PATCH v2 1/5] fs: Use a percpu_counter to track nr

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Message-ID: <493100B7.2010703@cosmosbay.com>
Date:	Sat, 29 Nov 2008 09:43:35 +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 1/5] fs: Use a percpu_counter to track nr_dentry

Adding a percpu_counter nr_dentry avoids cache line ping pongs
between cpus to maintain this metric, and dcache_lock is
no more needed to protect dentry_stat.nr_dentry

We centralize nr_dentry updates at the right place :
- increments in d_alloc()
- decrements in d_free()

d_alloc() can avoid taking dcache_lock if parent is NULL

(socket8 bench result : 27.5s to 25s)

Signed-off-by: Eric Dumazet <dada1@...mosbay.com>
---
 fs/dcache.c        |   49 +++++++++++++++++++++++++------------------
 include/linux/fs.h |    2 +
 kernel/sysctl.c    |    2 -
 3 files changed, 32 insertions(+), 21 deletions(-)

View attachment "nr_dentry.patch" of type "text/plain" (4892 bytes)