netdev - Re: [PATCH 1/3] sysfs directory scaling: rbtree for dirent name lookups

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Message-ID: <m1ocnjdh5q.fsf@fess.ebiederm.org>
Date:	Tue, 03 Nov 2009 02:41:37 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Benjamin LaHaise <bcrl@...et.ca>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Octavian Purdila <opurdila@...acom.com>,
	netdev@...r.kernel.org, Cosmin Ratiu <cratiu@...acom.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] sysfs directory scaling: rbtree for dirent name lookups

Benjamin LaHaise <bcrl@...et.ca> writes:

> Use an rbtree in sysfs_dirent to speed up file lookup times
>
> Systems with large numbers (tens of thousands and more) of network 
> interfaces stress the sysfs code in ways that make the linear search for 
> a name match take far too long.  Avoid this by using an rbtree.

Please take a look at the cleanups_scaling branch at:
kernel.org:/pub/scm/linux/kernel/git/ebiederm/linux-2.6.32-rc5-sysfs-enhancements

I haven't spent a lot of time on it but it is possible to get everything
except the rbtree without increasing the size of sysfs_dirent.  Also we
don't need the both the rbtree and a linked list.

In particular see:
commit 50623bbb82da3bd1d596b9173a91ed1b5aa168b8
Author: Eric W. Biederman <ebiederm@...well.aristanetworks.com>
Date:   Sat Oct 31 04:11:18 2009 -0700

    sysfs: Sort sysfs directories by name hash.
    
    This is a step in preparation for introducing a more efficient
    data structure than a linked list for sysfs entries.  By ordering
    by name hash instead of by inode sysfs_lookup can be speeded
    up as well as allowing restarting after seekdir.
    
    Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>

Meanwhile back to pushing the most important ones for real.

Eric
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