Re: [Qemu-devel] High speed polling

[Mulyadi Santosa]

Hi Clay.....

On Wed, Jun 15, 2011 at 05:32, Clay Andreasen <address@hidden> wrote:
> I have a network device simulation that I am connecting to multiple
> instances of Qemu (nodes) via a shared memory queue.  It works pretty well
> as
> long as all of the nodes are initiating communication but when one node is
> passive, it must poll to get packets.  So far the fastest I have been able
> to
> get it to poll is about every 2M emulated clocks.

that means, once every ... 1 mili second? (I doubt it, but
theoritically possible)

> This is with CONFIG_HIGH_RES_TIMERS and CONFIG_NO_HZ on the host.
> I also set MIN_TIMER_REARM_NS in qemu-timer.c to 100000.
> Is there some way to increase the polling rate by about an order of
> magnitude?

with the way current kernel did fair scheduling, your problem is
timing handling latency actually i.e timer is fast, but the handler
needs some time to catch up.

what I can suggest is experimenting with rt- kernel and put yourself
into such high priority process with realtime scheduling, keep
reducing MIN_TIMER_REARM_NS..

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com