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

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Message-ID: <51891095.4070008@suse.cz>
Date:	Tue, 07 May 2013 16:32:53 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	"Myklebust, Trond" <Trond.Myklebust@...app.com>,
	Jiri Slaby <jirislaby@...il.com>
CC:	"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 05/07/2013 04:27 PM, Myklebust, Trond wrote:
> 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?

Because we have the patch still in _3.9_. Dropped now in favor of the
commit below.

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

Thanks for letting me know.

-- 
js
suse labs
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