linux-kernel - Re: [PATCH 09/15] Make selection of 'readdir-plus' adapt to usage patterns.

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Date:	Tue, 7 May 2013 14:27:54 +0000
From:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
To:	Jiri Slaby <jslaby@...e.cz>
CC:	"jirislaby@...il.com" <jirislaby@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	NeilBrown <neilb@...e.de>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>
Subject: Re: [PATCH 09/15] Make selection of 'readdir-plus' adapt to usage
 patterns.

On Tue, 2013-05-07 at 16:18 +0200, Jiri Slaby wrote:
> From: NeilBrown <neilb@...e.de>
> 
> While the use of READDIRPLUS is significantly more efficient than
> READDIR followed by many GETATTR calls, it is still less efficient
> than just READDIR if the attributes are not required.
> 
> We can get a hint as to whether the application requires attr information
> by looking at whether any ->getattr calls are made between
> ->readdir calls.
> If there are any, then getting the attributes seems to be worth while.
> 
> This patch tracks whether there have been recent getattr calls on
> children of a directory and uses that information to selectively
> disable READDIRPLUS on that directory.
> 
> The first 'readdir' call is always served using READDIRPLUS.
> Subsequent calls only use READDIRPLUS if there was a getattr on a child
> in the mean time.
> 
> The locking of ->d_parent access needs to be reviewed.
> As the bit is simply a hint, it isn't critical that it is set
> on the "correct" parent if a rename is happening, but it is
> critical that the 'set' doesn't set a bit in something that
> isn't even an inode any more.
> 
> Acked-by: NeilBrown <neilb@...e.de>
> Signed-off-by: Neil Brown <neilb@...e.de>
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Cc: Trond Myklebust <Trond.Myklebust@...app.com>
> Cc: linux-nfs@...r.kernel.org
> ---

Why am I being Cced on this?

You have looked at commit d69ee9b85541a69a1092f5da675bd23256dc62af (NFS:
Adapt readdirplus to application usage patterns) which was upstreamed in
Linux 3.5, right?

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com
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