From: Paolo Bonzini <pbonzini@redhat.com>
To: Richard Laager <rlaager@wiktel.com>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations
Date: Thu, 15 Mar 2012 10:36:23 +0100 [thread overview]
Message-ID: <4F61B817.2010702@redhat.com> (raw)
In-Reply-To: <1331772155.24052.849.camel@watermelon.coderich.net>
Il 15/03/2012 01:42, Richard Laager ha scritto:
>> > It is worse in that we do not want the hardware parameters exposed to the
>> > guest to change behind the scenes, except if you change the machine type
>> > or if you use the default unversioned type.
> You're saying that discard_granularity and discard_zeros_data need to be
> properties of the machine type? If you start with that as a requirement,
> I can see why you want to always report discard_granularity=512 &
> discard_zeros_data=1. But that design has many downsides. I'm not
> convinced that discard_granularity and discard_zeros_data need to be
> properties of the machine type. Why do you feel that's necessary? What's
> the harm in those properties changing across QEMU startups (i.e. guest
> boots)?
Changing across guest boots is a minor problem, but changing across
migration must be avoided at all costs.
BTW, after this discussion I think we can instead report
discard_granularity = 512 and discard_zeroes_data=0 and get most of the
benefit, at least on file-backed storage.
Paolo
next prev parent reply other threads:[~2012-03-15 9:36 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-08 17:15 [Qemu-devel] [RFC PATCH 00/17] Improvements around discard and write zeroes Paolo Bonzini
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 01/17] qemu-iotests: add a simple test for write_zeroes Paolo Bonzini
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 02/17] qed: make write-zeroes bounce buffer smaller than a single cluster Paolo Bonzini
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 03/17] block: add discard properties to BlockDriverInfo Paolo Bonzini
2012-03-09 16:47 ` Kevin Wolf
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 04/17] qed: implement bdrv_aio_discard Paolo Bonzini
2012-03-09 16:31 ` Kevin Wolf
2012-03-09 17:53 ` Paolo Bonzini
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 05/17] block: pass around qiov for write_zeroes operation Paolo Bonzini
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations Paolo Bonzini
2012-03-09 16:37 ` Kevin Wolf
2012-03-09 18:06 ` Paolo Bonzini
2012-03-10 18:02 ` Richard Laager
2012-03-12 12:27 ` Paolo Bonzini
2012-03-12 13:04 ` Kevin Wolf
2012-03-13 19:13 ` Richard Laager
2012-03-14 7:41 ` Paolo Bonzini
2012-03-14 12:01 ` Kevin Wolf
2012-03-14 12:14 ` Paolo Bonzini
2012-03-14 12:37 ` Kevin Wolf
2012-03-14 12:49 ` Paolo Bonzini
2012-03-14 13:04 ` Kevin Wolf
2012-03-24 15:33 ` Christoph Hellwig
2012-03-24 15:30 ` Christoph Hellwig
2012-03-26 19:40 ` Richard Laager
2012-03-27 10:20 ` Kevin Wolf
2012-03-24 15:29 ` Christoph Hellwig
2012-03-26 9:44 ` Daniel P. Berrange
2012-03-26 9:56 ` Christoph Hellwig
2012-03-15 0:42 ` Richard Laager
2012-03-15 9:36 ` Paolo Bonzini [this message]
2012-03-16 0:47 ` Richard Laager
2012-03-16 9:34 ` Paolo Bonzini
2012-03-24 15:27 ` Christoph Hellwig
2012-03-26 19:40 ` Richard Laager
2012-03-27 9:08 ` Christoph Hellwig
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 07/17] block: make high level discard operation always zero Paolo Bonzini
2012-03-08 17:55 ` Avi Kivity
2012-03-09 16:42 ` Kevin Wolf
2012-03-12 10:42 ` Avi Kivity
2012-03-12 11:04 ` Kevin Wolf
2012-03-12 12:03 ` Avi Kivity
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 08/17] block: kill the write zeroes operation Paolo Bonzini
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 09/17] ide: issue discard asynchronously but serialize the pieces Paolo Bonzini
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 10/17] ide/scsi: add discard_zeroes_data property Paolo Bonzini
2012-03-08 18:13 ` Avi Kivity
2012-03-08 18:14 ` Avi Kivity
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 11/17] ide/scsi: prepare for flipping the discard defaults Paolo Bonzini
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 12/17] ide/scsi: turn on discard Paolo Bonzini
2012-03-08 18:17 ` Avi Kivity
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 13/17] block: fallback from discard to writes Paolo Bonzini
2012-03-24 15:35 ` Christoph Hellwig
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 14/17] block: support FALLOC_FL_PUNCH_HOLE trimming Paolo Bonzini
2012-03-09 8:20 ` Chris Wedgwood
2012-03-09 8:31 ` Paolo Bonzini
2012-03-09 8:35 ` Chris Wedgwood
2012-03-09 8:40 ` Paolo Bonzini
2012-03-09 10:31 ` Stefan Hajnoczi
2012-03-09 10:43 ` Paolo Bonzini
2012-03-09 10:53 ` Stefan Hajnoczi
2012-03-09 10:57 ` Paolo Bonzini
2012-03-09 20:36 ` Richard Laager
2012-03-12 9:34 ` Paolo Bonzini
2012-03-24 15:40 ` Christoph Hellwig
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 15/17] raw: add get_info Paolo Bonzini
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 16/17] qemu-io: fix the alloc command Paolo Bonzini
2012-03-08 17:15 ` [Qemu-devel] [RFC PATCH 17/17] raw: implement is_allocated Paolo Bonzini
2012-03-24 15:42 ` Christoph Hellwig
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