linux-kernel - Re: [patch] epoll use a single inode ...

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Message-Id: <200703081042.21454.dada1@cosmosbay.com>
Date:	Thu, 8 Mar 2007 10:42:21 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Davide Libenzi <davidel@...ilserver.org>,
	Avi Kivity <avi@...o.co.il>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [patch] epoll use a single inode ...

On Thursday 08 March 2007 09:56, Christoph Hellwig wrote:
> This patch needs a lot more documentation.  It needs some really big
> comments on why this should never ever be used for a real filesystem
> (real as in user mountable), and probably add an assert for that
> invariant somewhere.  Please also update Documentation/filesystems/Locking
> and Documentation/filesystems/vfs.txt for it.

Thank you for your feedback Christoph

Here is the version I was about to push to -mm, so if nobody complains, I ask 
Andrew to push it to mm so that it can reach 2.6.22 target

[PATCH] Delay the dentry name generation on sockets and pipes.

1) Introduces a new method in 'struct dentry_operations'. This method called 
d_dname() might be called from d_path() to build a pathname 
for special filesystems. It is called without locks.

Future patches (if we succeed in having one common dentry for all pipes) may 
need to change prototype of this method, but we now use :
char *d_dname(struct dentry *dentry, char *buffer, int buflen)


2) Use this new method for sockets : No more sprintf() at socket creation. 
This is delayed up to the moment someone does an access to /proc/pid/fd/...

3) Use this new method for pipes : No more sprintf() at pipe creation. This is 
delayed up to the moment someone does an access to /proc/pid/fd/...

A benchmark consisting of 1.000.000 calls to pipe()/close()/close() gives a 
*nice* speedup on my Pentium(M) 1.6 Ghz :

3.090 s instead of 3.450 s

Signed-off-by: Eric Dumazet <dada1@...mosbay.com>
CC: Christoph Hellwig <hch@...radead.org>
CC: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Davide Libenzi <davidel@...ilserver.org>
CC: Al Viro <viro@...iv.linux.org.uk>

 Documentation/filesystems/Locking |    2 ++
 Documentation/filesystems/vfs.txt |   12 +++++++++++-
 fs/dcache.c                       |    3 +++
 fs/pipe.c                         |   12 +++++++++---
 include/linux/dcache.h            |    1 +
 net/socket.c                      |   13 ++++++++++---
 6 files changed, 36 insertions(+), 7 deletions(-)

View attachment "introduce_d_dname.patch" of type "text/plain" (5326 bytes)