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Re: [Qemu-devel] buffer alignment for block backends
From: |
Stefano Stabellini |
Subject: |
Re: [Qemu-devel] buffer alignment for block backends |
Date: |
Thu, 09 Apr 2009 10:57:03 +0100 |
User-agent: |
Thunderbird 2.0.0.14 (X11/20080505) |
Anthony Liguori wrote:
>> If you do not want to do that, another possible solution is to create a
>> new function called "qemu_blockalign" that would be implemented as
>> qemu_memalign(512, size);
>
> This is fine, but this is purely an optimization, it cannot be relied
> upon in the general case.
well, there aren't many places that allocate buffers for the block
backends, I can count only the following for dma operations:
- block.c:bdrv_aio_rw_vector
and this one for other ide read and write operations:
- ide.c:ide_init2
I think it would be important at least for dma operations.
>> so we don't have to write 512 bytes everywhere
>> but only in one place, thus making life easier to people like me that
>> have to change the value for a special case.
>>
>> Thanks in advance for your sympathy :)
>>
>
> Why does your backend requirement page alignment and who's notion of page?
>
my backend (block-vbd) needs page aligned buffers because blkfront needs
page aligned buffers. I could allocate a new page aligned buffer every
time and the memcpy but it is just a waste.
The notion of page is the host notion of page (minios in this case).
- [Qemu-devel] buffer alignment for block backends, Stefano Stabellini, 2009/04/08
- Re: [Qemu-devel] buffer alignment for block backends, Anthony Liguori, 2009/04/08
- Re: [Qemu-devel] buffer alignment for block backends,
Stefano Stabellini <=
- Re: [Qemu-devel] buffer alignment for block backends, Anthony Liguori, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Stefano Stabellini, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Gerd Hoffmann, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Samuel Thibault, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Stefano Stabellini, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Gerd Hoffmann, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Stefano Stabellini, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Samuel Thibault, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Anthony Liguori, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Jamie Lokier, 2009/04/09