Date: Fri, 23 Apr 2010 08:08:50 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Andriy Gapon <avg@icyb.net.ua> Cc: freebsd-fs@FreeBSD.org, freebsd-geom@FreeBSD.org Subject: Re: vdev_geom_io: parallelize ? Message-ID: <20100423060850.GB1670@garage.freebsd.pl> In-Reply-To: <4BD0C802.3000004@icyb.net.ua> References: <4BD0C802.3000004@icyb.net.ua>
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On Fri, Apr 23, 2010 at 01:04:50AM +0300, Andriy Gapon wrote:
>=20
> Just thinking out loud.
>=20
> Currently ZFS vdev_geom_io does something like:
> for (...) {
> ...
> g_io_request(...);
> biowait(...);
> ...
> }
> I/O is done in MAXPHYS chunks.
>=20
> 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.
--=20
Pawel Jakub Dawidek http://www.wheelsystems.com
pjd@FreeBSD.org http://www.FreeBSD.org
FreeBSD committer Am I Evil? Yes, I Am!
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