linux-kernel - Re: [PATCH 3/7] sysfs: Keep an nlink count on sysfs directories.

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Date:	Tue, 12 Jan 2010 09:46:59 +0900
From:	Tejun Heo <tj@...nel.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Greg Kroah-Hartman <gregkh@...e.de>,
	Kay Sievers <kay.sievers@...y.org>,
	linux-kernel@...r.kernel.org,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	linux-fsdevel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Benjamin LaHaise <bcrl@...et.ca>,
	Serge Hallyn <serue@...ibm.com>,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: Re: [PATCH 3/7] sysfs: Keep an nlink count on sysfs directories.

Hello,

On 01/12/2010 05:21 AM, Eric W. Biederman wrote:
> On large directories sysfs_count_nlinks can be a significant
> bottleneck, so keep a count in sysfs_dirent.

I was about to suggest changing s_flags to ushort too.  Hmmm... adding
a new field to sysfs_dirent somewhat worries me but this doesn't add
to the size of the structure.  How significant bottlenect are we
talking about?

> If we exceed the maximum number of directory entries we can store
> return nlink of 1.  An nlink of 1 matches what reiserfs does in this
> case, and it let's find and similar utlities know that we have a the
> directory nlink can not be used for optimization purposes.

Hmmm... what's the limit on reiserfs?  Is it 64k too?

Thanks.

-- 
tejun
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