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Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on c
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert |
Date: |
Fri, 19 Jul 2013 07:58:11 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 |
Il 18/07/2013 21:28, Peter Lieven ha scritto:
> thanks for the details. I think to have optimal performance and best
> change for unmapping in qemu-img convert
> it might be best to export the OPTIMAL UNMAP GRANULARITY
Agreed about this.
> as well as the write_zeroes_w_discard capability via the BDI
But why this?!? It is _not_ needed. All you need is to change the
default of the "-S" option to be the OPTIMAL UNMAP GRANULARITY if it is
nonzero.
Paolo
> and than zero
> out the whole device with bdrv_write_zeroes and the BDRV_MAY_DISCARD
> flag.
>
> the logic for this is already prepared in patch4 (topic of this email).
> except that
> i have to exchange bdrv_discard with bdrv_write_zeroes w/ BDRV_MAY_DISCARD.
>
> what do you think?
>
>
>
>>
>>
>> On Thu, Jul 18, 2013 at 11:43 AM, Peter Lieven <address@hidden> wrote:
>>>
>>> Am 18.07.2013 um 16:35 schrieb Paolo Bonzini <address@hidden>:
>>>
>>>> Il 18/07/2013 16:32, Peter Lieven ha scritto:
>>>>>>>
>>>>>> (Mis)alignment and granularity can be handled later. We can ignore them
>>>>>> for now. Later, if we decide the best way to support them is a flag,
>>>>>> we'll add it. Let's not put the cart before the horse.
>>>>>>
>>>>>> BTW, I expect alignment!=0 to be really, really rare.
>>>>> To explain my concerns:
>>>>>
>>>>> I know that my target has internal page size of 15MB. I will check what
>>>>> happens
>>>>> if I deallocate this 15MB in chunks of lets say 1MB. If the page gets
>>>>> unprovisioned
>>>>> after the last chunk is unmapped it would be fine :-)
>>>>
>>>> You're talking of granularity here, not (mis)alignment.
>>>
>>> you are right. for the target i am talking about this is 30720 512-byte
>>> blocks for the granularity (pagesize) and 0 for the alignment.
>>> i will see what happens if I write same w/unmap the whole 30720 blocks in
>>> smaller blocks ;-) otherwise i will have to add support for honoring this
>>> values in qemu-img convert
>>> as a follow up.
>>>
>>> Peter
>>>
>
>
>
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, (continued)
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Paolo Bonzini, 2013/07/18
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Peter Lieven, 2013/07/18
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Paolo Bonzini, 2013/07/18
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Peter Lieven, 2013/07/18
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Paolo Bonzini, 2013/07/18
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Peter Lieven, 2013/07/18
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Paolo Bonzini, 2013/07/18
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Peter Lieven, 2013/07/18
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, ronnie sahlberg, 2013/07/18
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Peter Lieven, 2013/07/18
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Peter Lieven, 2013/07/19
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, ronnie sahlberg, 2013/07/19
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Peter Lieven, 2013/07/19
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, ronnie sahlberg, 2013/07/19
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Peter Lieven, 2013/07/19
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, ronnie sahlberg, 2013/07/19
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, ronnie sahlberg, 2013/07/18
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Paolo Bonzini, 2013/07/18
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, ronnie sahlberg, 2013/07/17
- Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert, Kevin Wolf, 2013/07/18