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Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for
From: |
Richard Laager |
Subject: |
Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations |
Date: |
Mon, 26 Mar 2012 14:40:48 -0500 |
On Sat, 2012-03-24 at 16:30 +0100, Christoph Hellwig wrote:
> On Wed, Mar 14, 2012 at 01:14:18PM +0100, Paolo Bonzini wrote:
> >
> > Note that the discard granularity is only a hint, so it's really more a
> > maximum suggested value than a granularity. Outside of a cluster
> > boundary the format would still have to write zeros manually.
> >
> > Also, Linux for example will only round the number of sectors down to
> > the granularity, not the start sector.
>
> Which really is more of a bug than a feature. The current discard
> implementation in Linux is still very poor.
The disk protocols do not require the granularity to be respected. It is
*only a hint*. Therefore, QEMU has to handle non-aligned discards. It
doesn't really matter what we wish was the case; this is the reality.
--
Richard
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- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, (continued)
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Kevin Wolf, 2012/03/12
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Richard Laager, 2012/03/13
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Paolo Bonzini, 2012/03/14
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Kevin Wolf, 2012/03/14
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Paolo Bonzini, 2012/03/14
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Kevin Wolf, 2012/03/14
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Paolo Bonzini, 2012/03/14
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Kevin Wolf, 2012/03/14
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Christoph Hellwig, 2012/03/24
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Christoph Hellwig, 2012/03/24
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations,
Richard Laager <=
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Kevin Wolf, 2012/03/27
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Christoph Hellwig, 2012/03/24
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Daniel P. Berrange, 2012/03/26
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Christoph Hellwig, 2012/03/26
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Richard Laager, 2012/03/14
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Paolo Bonzini, 2012/03/15
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Richard Laager, 2012/03/15
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Paolo Bonzini, 2012/03/16
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Christoph Hellwig, 2012/03/24
- Re: [Qemu-devel] [RFC PATCH 06/17] block: use bdrv_{co, aio}_discard for write_zeroes operations, Richard Laager, 2012/03/26