Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool

[Anthony Liguori <anthony@codemonkey.ws>]

Gerd Hoffmann wrote:
> Andrea Arcangeli wrote:
>   
>> On Fri, Dec 12, 2008 at 12:17:58PM -0600, Anthony Liguori wrote:
>>     
>>> You assume that anything using bdrv_aio_readv/writev will be going through 
>>> a DMA API.  This isn't a safe assumption.
>>>       
>> Well it's obviously a safe assumption right now... ;)
>>     
>
> Well, the xen block backend in my xen patch queue calls bdrv_* directly
> right now.  Dunno whenever it is possible/useful to fit the grant table
> stuff into the upcoming dma api somehow.
>   

I don't know about grant table references b/c that's really foreign 
memory.  But this is a good argument against the DMA as it stands, b/c 
you may be handing foreign memory to bdrv_aio_readv/writev.

A big reason for the map/unmap lock/unlock abstraction though would be 
the qemu-dm map cache.  I think you could use it to pretty reasonably 
integrate the map cache which I know I've previously could never be done :-)

Regards,

Anthony Liguori

> cheers,
>   Gerd
>
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