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Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes |
Date: |
Mon, 24 Feb 2014 20:04:13 +0800 |
User-agent: |
Mutt/1.5.22 (2013-10-16) |
On Mon, 02/24 12:51, Paolo Bonzini wrote:
> Il 24/02/2014 12:33, Fam Zheng ha scritto:
> >> This is (or should be) bdrv_co_write_zeroes without BDRV_REQ_MAY_UNMAP.
> >
> >But IIUC bdrv_co_write_zeroes without BDRV_REQ_MAY_UNMAP doesn't require
> >cluster allocation if it's allocated yet, which is a bit different.
>
> Yeah, that's why I wrote "or should be". Those are the intended semantics
> of bdrv_co_write_zeroes without BDRV_REQ_MAY_UNMAP: always allocate a
> cluster that will read as zeroes (allocating even if it does not necessarily
> write the zeroes).
>
> For legacy reasons it may not be exactly what is implemented. I asked Kevin
> a couple of weeks ago and he sent a patch, but even he wasn't sure of what
> qcow2 was doing util he looked at the code. :)
>
I see. I could only tell in VMDK cluster doesn't have this "mapped and zeroed"
state, so maybe we need some flexibility here and reduce assumption.
Fam
- [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Peter Lieven, 2014/02/22
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Fam Zheng, 2014/02/22
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Peter Lieven, 2014/02/23
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Fam Zheng, 2014/02/23
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Paolo Bonzini, 2014/02/24
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Fam Zheng, 2014/02/24
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Paolo Bonzini, 2014/02/24
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes,
Fam Zheng <=
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Kevin Wolf, 2014/02/24
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Paolo Bonzini, 2014/02/24
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Kevin Wolf, 2014/02/24
Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Kevin Wolf, 2014/02/24
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Peter Lieven, 2014/02/24
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Paolo Bonzini, 2014/02/24
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Peter Lieven, 2014/02/24
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Peter Lieven, 2014/02/24
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Kevin Wolf, 2014/02/25
- Re: [Qemu-devel] [RFC PATCH] block: optimize zero writes with bdrv_write_zeroes, Peter Lieven, 2014/02/25