From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:60002)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1Vfvnm-0003oE-V6
	for qemu-devel@nongnu.org; Mon, 11 Nov 2013 13:01:36 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1Vfvng-0004Pl-W2
	for qemu-devel@nongnu.org; Mon, 11 Nov 2013 13:01:30 -0500
Received: from mx1.redhat.com ([209.132.183.28]:15252)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1Vfvng-0004PR-N7
	for qemu-devel@nongnu.org; Mon, 11 Nov 2013 13:01:24 -0500
Message-ID: <52811B60.8080202@redhat.com>
Date: Mon, 11 Nov 2013 19:01:04 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
MIME-Version: 1.0
References: <1383560924-15788-1-git-send-email-matthias.bgg@gmail.com>
	<20131105132509.GC16457@stefanha-thinkpad.redhat.com>
	<CABuKBeKECgN8D+hn8UM3nXFCO8nj-+16NGzB8B=EHMx7K+xq3Q@mail.gmail.com>
	<20131111124329.GA1036@stefanha-thinkpad.redhat.com>
	<E61CAC10-9C90-495F-8AE2-549E368508FD@alex.org.uk>
In-Reply-To: <E61CAC10-9C90-495F-8AE2-549E368508FD@alex.org.uk>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH v2 0/3] Make thread pool implementation
	modular
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Alex Bligh <alex@alex.org.uk>
Cc: Kevin Wolf <kwolf@redhat.com>, Liu Ping Fan <pingfank@linux.vnet.ibm.com>, Stefan Hajnoczi <stefanha@redhat.com>, Stefan Hajnoczi <stefanha@gmail.com>, Jeff Cody <jcody@redhat.com>, Michael Tokarev <mjt@tls.msk.ru>, qemu-devel@nongnu.org, Markus Armbruster <armbru@redhat.com>, malc <av1474@comtv.ru>, Anthony Liguori <anthony@codemonkey.ws>, Stefan Weil <sw@weilnetz.de>, Matthias Brugger <matthias.bgg@gmail.com>, Asias He <asias@redhat.com>, Luiz Capitulino <lcapitulino@redhat.com>, =?ISO-8859-1?Q?Andreas_F=E4rber?= <afaerber@suse.de>, Eduardo Habkost <ehabkost@redhat.com>

Il 11/11/2013 18:59, Alex Bligh ha scritto:
> > Why is it necessary to push this task down into the host?  I don't
> > understand the advantage of this approach except that maybe it works
> > around certain misconfigurations, I/O scheduler quirks, or plain old
> > bugs - all of which should be investigated and fixed at the source
> > instead of adding another layer of code to mask them.
> 
> I can see an argument why a guest with two very differently
> performing disks attached might be best served by two worker
> threads, particularly if one such thread was in part CPU bound
> (inventing this use case is left as an exercise for the reader).

In most cases you want to use aio=native anyway, and then the QEMU
thread pool is entirely bypassed.

Paolo