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Message-ID: <4F69A798.4000200@ce.jp.nec.com>
Date: Wed, 21 Mar 2012 19:04:08 +0900
From: "Jun'ichi Nomura" <j-nomura@...jp.nec.com>
To: device-mapper development <dm-devel@...hat.com>,
Mikulas Patocka <mpatocka@...hat.com>
CC: "Alasdair G. Kergon" <agk@...hat.com>,
Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Subject: Re: [dm-devel] [PATCH] Fix I/O counts in vmstat
Hi Mikulas,
> The decision whether bio is counted or not is made by the code that
> submits the bio. This leads to some problems:
How about convering dm targets to use generic_make_request?
Since submit_bio counts vm events, it seems natural for
caller to decide which function to use.
Device driver does not know whether the requested I/O is
for vm-to-device or device-to-device.
We could still use iostat to measure throughput of individual
block devices.
Thanks,
--
Jun'ichi Nomura, NEC Corporation
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