Re: [Qemu-devel] [RFC] [PATCHv8 09/30] aio / timers: Add QEMUTimerListGroup and helper functions

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

于 2013-8-10 19:05, Alex Bligh 写道:
> Paolo,
>
> On 9 Aug 2013, at 15:59, Paolo Bonzini wrote:
>
>> It's not papering over anything.
>>
>> Timers right now are provided by the event loop.  If you make
>> AioContexts have timers, you can have a new AioContext for the timers
>> that the event loop handles before your patches.
>>
>> It's not related to having two nested event loops.  The nested event
>> loops have the problem that timers do not run in them, but it's also a
>> feature---because you know exactly what code runs in the nested event
>> loop and what doesn't.  Using an entirely distinct event loop preserves
>> the feature.
>
> I've submitted a first cut as a separate patch just to see whether
> it works:
>    http://lists.nongnu.org/archive/html/qemu-devel/2013-08/msg01412.html
>
> It passes 'make check' anyway.
>
> I didn't wrap TimerListGroup into a separate struct for reasons
> I'll set out below.
>
> I think there are two ways to go here:
>
> 1. Wrap TimerListGroup into a separate struct, leave all the
>     TimerListGroup functions in. This probably makes it easier if
>     (for instance) we decided to get rid of AioContexts entirely
>     and make them g_source subclasses (per Wenchao Xia).
>
   I have a quick view of this series, but not very carefully since
it is quite long.:) I have replied with Paolo's comments on my
RFC thread. Personally I like g_source sub class, which make code
clear, but let's discuss first if the direction is right in that mail.


> 2. Remove the TimerListGroup thing entirely and just have
>     an array of TimerLists of size QEMU_CLOCK_MAX. I can
>     leave the things that iterate that array inside qemu_timer.c
>     (which I'd rather do for encapsulation). Part of the
>     problem with the old timer code was that there were (in
>     my opinion) far too many files that were working out what
>     to iterate, and I really don't want to reintroduce that.
>
> Despite the fact we both dislike the name TimerListGroup, I
> think the way to go here is (1). (2) does not really save lines
> of code (certainly not compiled instructions) - it's main saving
> is removing a pile of commenting from include/qemu/timer.h,
> which makes things more opaque.
>
> I also think there may well be a use for something that wants
> to use timers but not AioContext (I am thinking for instance
> of a thread that does not do block IO). This permits that,
> but does not require it.
>
> WDYT?
>


-- 
Best Regards

Wenchao Xia