Re: [Qemu-devel] [RFC 0/8] arm AioContext with its own timer stuff

[liu ping fan]

On Sun, Jul 21, 2013 at 5:53 PM, Alex Bligh <address@hidden> wrote:
> Liu,
>
>
> --On 21 July 2013 16:42:57 +0800 Liu Ping Fan <address@hidden> wrote:
>
>> Currently, the timers run on iothread within BQL, so virtio-block
>> dataplane can not use throttle, as Stefan Hajnoczi pointed out in his
>> patches to port dataplane onto block layer.(Thanks, Stefan) To enable
>> this feature, I plan to enable timers to run on AioContext's thread. And
>> maybe in future, hpet can run with its dedicated thread too.
>>
>> Also, I see Alex Bligh is on the same effort by another method,(it is a
>> good idea)    "[RFC] aio/async: Add timed bottom-halves".
>
>
> Stefan & Paolo did not like that method much, so I did a third method
> (posted yesterday) suggested by Stefan which adds a clock to AioContext (to
> which timers can be attached), deletes ALL the alarm_timer stuff (which was
> very cathartic), uses timeouts on the g_poll, and adds ppoll where this is
> available. Series at:
>  http://lists.nongnu.org/archive/html/qemu-devel/2013-07/msg03334.html
>
> I suspect this also overlaps with your code.
>
> So now we have 3 methods to do similar things!
>
> One advantage of my approach is that it removes more code than it adds
> (by quite a margin). However, alarm timers could have been left in.
> What's the advantage in giving an AioContext its own alarm timer as
> opposed to just its own clock?
>
I read your second series, and try to summary the main different between us.
Please correct me, if I misunderstood something.
--1st. You try to create a separate QemuClock for AioContext.
    I think QemuClock is the clock event source and we have three
classic with fine definition. They should be qemu-wide for time
measurement.  On the other handler, timer is  a concept for timeout,
so it can be AioContext-related. So I have patch2&5.
--2nd. You want to substitute alarm_timer with timeout of poll.
    I try to trigger each specified thread when its deadline comes.
But unfortunately, the signal can not be delivered to the specified
thread directly, and I need timerfd for each AioContext. (If we can
have the equivalent on other platform)

Anything else?

Thanks and regards,
Pingfan

> --
> Alex Bligh