Re: [Qemu-devel] [PATCH] main-loop: Don't lock starve io-threads when main_loop_tlg has pending events

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 10/08/2013 09:33 PM, Alex Bligh wrote:
>
> On 8 Oct 2013, at 20:21, Hans de Goede wrote:
>
>> Wasn't it 1 ms until the offending commit (note 250 us does
>> sound better to me).
>
> I believe you've made it 1 nanosecond not 1 millisecond;

Correct, the 1 ms I referred to was before your commit which changed
things from ms to ns.

> can that be right?

The purpose of the 1 ns timeout is to cause os_host_main_loop_wait
to unlock the iothread, as $subject says the problem I'm seeing seems
to be lock starvation not cpu starvation.

Note as I already indicated I'm in no way an expert in this, if you
and or Paolo suspect cpu starvation may happen too, then bumping
the timeout to 250 us is fine with me too.

If we go with 250 us that thus pose the question though if we should
always keep a minimum timeout of 250 us when not non-blocking, or only
bump it to 250 us when main_loop_tlg has already expired events and
thus is causing a timeout of 0.

Regards,

Hans