Re: [Qemu-devel] [RFC PATCH v2 0/4] port network layer onto glib

[liu ping fan]

On Mon, Apr 8, 2013 at 7:46 PM, Stefan Hajnoczi <address@hidden> wrote:
> On Tue, Apr 02, 2013 at 05:49:57PM +0800, liu ping fan wrote:
>> On Thu, Mar 28, 2013 at 9:40 PM, Stefan Hajnoczi <address@hidden> wrote:
>> > On Thu, Mar 28, 2013 at 09:42:47AM +0100, Paolo Bonzini wrote:
>> >> Il 28/03/2013 08:55, Liu Ping Fan ha scritto:
>> >> >    3rd. block layer's AioContext will block other AioContexts on the 
>> >> > same thread.
>> >>
>> >> I cannot understand this.
>> >
>> > The plan is for BlockDriverState to be bound to an AioContext.  That
>> > means each thread is set up with one AioContext.  BlockDriverStates that
>> > are used in that thread will first be bound to its AioContext.
>> >
>> > It's not very useful to have multiple AioContext in the same thread.
>> >
>> But it can be the case that we detach and re-attach the different
>> device( AioContext) to the same thread.   I think that the design of
>> io_flush is to sync, but for NetClientState, we need something else.
>> So if we use AioContext, is it proper to extend readable/writeable
>> interface for qemu_aio_set_fd_handler()?
>
> Devices don't have AioContexts, threads do.  When you bind a device to
> an AioContext the AioContext already exists independent of the device.
>
Oh, yes.  So let me say in this way,   switch the devices among
different thread. Then if NetClientState happens to exist on the same
thread with BlockDriverState, it will not be responsive until the
BlockDriverState has finished the flying job.

> Unfortunately I don't understand your question about io_flush and
> readable/writeable qemu_aio_set_fd_handler().
>
As for readable/writable, I mean something like IOCanReadHandler. If
NetClientState is unreadable, it just does not poll for G_IO_IN event,
but not blocks.  But as for io_flush, it will block for pending AIO
operations. These behaviors are different, so I suggest to expand
readable/writeable for qemu_aio_set_fd_handler()

Regards,
Pingfan

> Stefan