Re: [Qemu-devel] GSoC: Improved image format compatibility

[Lyu Mitnick <mitnick.lyu@gmail.com>]

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Hello

I have some question about asynchronous i/o in QEMU block driver: Why a file
format with asynchronous i/o support(ex. qcow) doesn't need to register
bdrv_read/bdrv_write which is registered in vhd file format?? Would qcow
block driver
also support synchronous i/o??

thanks a lot

Mitnick

2011/4/2 Kevin Wolf <kwolf@redhat.com>

> Am 01.04.2011 17:15, schrieb Lyu Mitnick:
> > Hello Stefan
> >
> >     Hello Mitnick,
> >
> >     asynchronous i/o is also missing in block/vpc.c.
> >
> >     All newer block drivers support asynchronous reads and writes,
> >     only some old drivers don't.
> >
> >     So adding asynchronous i/o to at least some of the old drivers
> >     would improve their usability.
> >
> >     Look for "aio" in block/*.c to get a starting point.
> >
> >     Regards
> >     Stefan (W.)
> >
> >
> > I look for "aio" in block/*.c as a starting point of asynchronous i/o.
> > And I
> > found that there isn't any "aio" keywords in block/vmdk.c. block/vmdk.c
> > is used as block driver for the VMDK format. Is it means that
> asynchronous
> > i/o is also missing in VMDK format?
>
> Yes, the VMDK implementation is completely synchronous.
>
> Kevin
>

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