linux-kernel - Re: [patch 01/27] fs: cleanup files

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Message-ID: <20090426061227.GA28555@wotan.suse.de>
Date:	Sun, 26 Apr 2009 08:12:27 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Al Viro <viro@...IV.linux.org.uk>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [patch 01/27] fs: cleanup files_lock

On Fri, Apr 24, 2009 at 10:35:10PM -0700, Eric W. Biederman wrote:
> npiggin@...e.de writes:
> 
> > Lock tty_files with tty_mutex, provide helpers to manipulate the per-sb
> > files list, and unexport the files_lock spinlock.
> 
> This conflicts a bit with some of my ongoing work, which is generalizing
> the file list to make it more useful and makes the tty case much less
> of a special case.

OK. My first patch should be fine, though.

 
> Do you know if the performance improvement would be anywhere near as good if
> file_list and file_list_lock becoming per inode?

Interesting (I didn't look closely at your patches yet). Probably that
would be quite reasonable.

 
> Do you have any idea what the performance improvement with changing the file_list_lock
> is?

Several of these locks hit in the same workloads so they mask each
other. I only just got the patchset to the stage where I can really
benchmark it. I could try your alternative as well.


 
> > Index: linux-2.6/fs/open.c
> > ===================================================================
> > --- linux-2.6.orig/fs/open.c
> > +++ linux-2.6/fs/open.c
> > @@ -828,7 +828,7 @@ static struct file *__dentry_open(struct
> >  	f->f_path.mnt = mnt;
> >  	f->f_pos = 0;
> >  	f->f_op = fops_get(inode->i_fop);
> > -	file_move(f, &inode->i_sb->s_files);
> > +	file_sb_list_add(f, inode->i_sb);
> 
> You can make this just:
> 	 if (!special_file(inode->i_mode))
> 		file_add(f, &inode->i_files);
> 
> And save yourself a lot of complexity.

Probably right, but I'll leave that for someone else to do.

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