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Date: Thu, 7 Mar 2002 12:48:39 +0100
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From: Christoph Hellwig <hch@ns.caldera.de>
To: cmm@us.ibm.com (mingming cao)
Cc: Jean-Eric Cuendet <jean-eric.cuendet@linkvest.com>,
        linux-kernel@vger.kernel.org, Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH] Rework of /proc/stat
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In article <3C86BEB0.4090203@us.ibm.com> you wrote:
>> Any reason for preferring this over the sard patches in -ac ?
>> 
> Basically, statistic data are moved from the global kstat structure

Why do you think sard uses kstat?

> to 
> the request_queue structures, and it is allocated/freed when the request 
> queue is initialized and freed.  This way it is

> 1)self-controlled;
> 2)avoid the lookup step before the accounting, so it should be faster;

in 2.4.18+ get_gendisk is O(1) - the lookup is not costly at all.

> 3)statistics implementation is not affected by the major/minor numbers;

Gendisks currently are per-major, which is a disadvantage, but the sard
code itself is not affected by that.

> 4)able to gathering statistics for all disks while keep the memory needs 
> minimized.

The same is true for sard.

Somehow I think you haven't actually looked at the sard code in -ac..

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