From: Matthew Wilcox <matthew@wil.cx>
To: Liuweni <qingshenlwy@gmail.com>
Cc: strongzgy <strongzgy@gmail.com>, xgr178 <xgr178@163.com>,
Liu Hui <onlyflyer@gmail.com>, viro <viro@zeniv.linux.org.uk>,
akpm <akpm@linux-foundation.org>, jack <jack@suse.cz>,
npiggin <npiggin@suse.de>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Re: [PATCH 1/3]fs/inode: iunique() Optimize Performance
Date: Tue, 1 Dec 2009 07:00:41 -0700 [thread overview]
Message-ID: <20091201140041.GW9482@parisc-linux.org> (raw)
In-Reply-To: <200912012115341872867@gmail.com>
On Tue, Dec 01, 2009 at 09:21:32PM +0800, Liuweni wrote:
> Hi Matthew Wilcox:
> I got the code note as the following. if there is no performance problem,
> maybe the code note need update.
>
>
> ------
> * BUGS:
> * With a large number of inodes live on the file system this function
> * currently becomes quite slow.
>
I don't believe that comment is correct. In any case, your optimisation
wouldn't make a lick of difference to the speed; it's a single comparison
in a loop which also calculates a hash, makes a function call, and walks
the length of a hash chain.
The old adage about debugging code, not comments applies here. Don't take
somebody else's word for it that there's a performance problem here.
Devise a test to demonstrate the performance problem. Otherwise, how
will you know if you solved it?
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
next prev parent reply other threads:[~2009-12-01 14:00 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-25 14:09 [PATCH 1/3]fs/inode: iunique() Optimize Performance Liuweni
2009-11-25 14:15 ` Matthew Wilcox
2009-11-25 19:20 ` Jérémy Cochoy
2009-11-25 19:52 ` Matthew Wilcox
2009-12-01 5:01 ` liu weni
2009-12-01 12:03 ` Matthew Wilcox
2009-12-01 13:21 ` Liuweni
2009-12-01 14:00 ` Matthew Wilcox [this message]
2009-12-02 9:42 ` Nick Piggin
2009-11-25 14:51 ` Liuweni
2009-11-25 14:54 ` Matthew Wilcox
2009-11-25 15:06 ` Andi Kleen
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