From owner-freebsd-fs@FreeBSD.ORG  Fri Apr 23 06:42:56 2010
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Date: Fri, 23 Apr 2010 09:42:53 +0300
From: Andriy Gapon <avg@icyb.net.ua>
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To: Pawel Jakub Dawidek <pjd@FreeBSD.org>
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Cc: freebsd-fs@FreeBSD.org, freebsd-geom@FreeBSD.org
Subject: Re: vdev_geom_io: parallelize ?
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on 23/04/2010 09:08 Pawel Jakub Dawidek said the following:
> On Fri, Apr 23, 2010 at 01:04:50AM +0300, Andriy Gapon wrote:
>> Just thinking out loud.
>>
>> Currently ZFS vdev_geom_io does something like:
>> for (...) {
>> 	...
>> 	g_io_request(...);
>> 	biowait(...);
>> 	...
>> }
>> I/O is done in MAXPHYS chunks.
>>
>> If that was changed to first issuing all the requests and only after that
>> waiting on them, could there be any performance benefit?
>> Or cases of vdev_geom_io with size > MAXPHYS are too rare?
>> Or something else?
> 
> The vdev_geom_io() function is there only to read ZFS labels, it is not
> used during regular I/O. Regular I/O requests are handled asynchronously
> by the vdev_geom_io_start() function.

Oops.  Thanks!

-- 
Andriy Gapon