From: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
To: "'Andrew Morton'" <akpm@osdl.org>
Cc: "linux-kernel" <linux-kernel@vger.kernel.org>
Subject: RE: [patch] add an iterator index in struct pagevec
Date: Mon, 4 Dec 2006 22:21:43 -0800
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Andrew Morton wrote on Monday, December 04, 2006 9:45 PM
> On Mon, 4 Dec 2006 21:21:31 -0800
> "Chen, Kenneth W" <kenneth.w.chen@intel.com> wrote:
> 
> > pagevec is never expected to be more than PAGEVEC_SIZE, I think a
> > unsigned char is enough to count them.  This patch makes nr, cold
> > to be unsigned char
> 
> Is that on the right side of the speed/space tradeoff?

I haven't measured speed.  Size wise, making them char shrinks vmlinux
text size by 112 bytes on x86_64 (using default config option).


> I must say I'm a bit skeptical about the need for this.  But I haven't
> looked closely at the blockdev-specific dio code yet.

It was suggested to declare another struct that embeds pagevec to perform
iteration.  But I prefer to have pagevec having the capability, it is
more compact this way.

It would be nice if you can review blockdev-specific dio code.  I would
appreciate it very much.

- Ken
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