Re: [Qemu-devel] [PATCH v4 00/10] main-loop: switch to g_poll(3) on POSIX hosts

[Jan Kiszka]

On 2013-02-21 18:10, Paolo Bonzini wrote:
> Il 21/02/2013 17:29, Jan Kiszka ha scritto:
>> In this context, I'd like to recall a detail: Real-time prioritization
>> of those I/O threads will most probably require locking with
>> prio-inversion avoidance (*). In that case external libs without a
>> chance to tune or replace their internal locking (like glib) will be a
>> no-go for those kind of I/O threads.
>>
>> The glib mainloop might be fine for all the rest, but we will likely
>> also need event loops with RT-compatible locking. So this refactoring
>> should keep the door open for alternative implementations.
> 
> Yes, this refactoring is fine.  It doesn't use the glib mainloop any
> more than before.  AioContext is fine as an RT-compatible event loop.
> You can use both as a GSource or manually from a separate thread.
> 
> What would be more problematic is the chardev flow control patches,
> which use the glib main loop directly.  I don't recall your KVM forum
> presentation---did you need RT prioritization of the serial port too?

Not in my use case (that was the RTC).

I didn't come across a scenario where you have to emulated a serial port
with real-time constraints so far but I would not exclude it. Hmm, think
of serial over LAN: UART device is remote, virtualized legacy system
shall talk to it as if it was locally connected, and that in a timely
manner.

Jan

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