* bad interaction between boosted idle vcpus and csched's tickling?
@ 2010-05-07 12:36 Jan Beulich
2010-05-07 13:02 ` Keir Fraser
2010-05-11 10:14 ` Keir Fraser
0 siblings, 2 replies; 3+ messages in thread
From: Jan Beulich @ 2010-05-07 12:36 UTC (permalink / raw)
To: Keir Fraser; +Cc: xen-devel
Keir,
isn't there a problem after the change to handle tasklets in idle vcpus
in that {default,acpi_processor}_idle() will put the vcpu to sleep with
boosted priority still in place, hence preventing it from being tickled
and/or needlessly tickling other CPUs?
Jan
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: bad interaction between boosted idle vcpus and csched's tickling?
2010-05-07 12:36 bad interaction between boosted idle vcpus and csched's tickling? Jan Beulich
@ 2010-05-07 13:02 ` Keir Fraser
2010-05-11 10:14 ` Keir Fraser
1 sibling, 0 replies; 3+ messages in thread
From: Keir Fraser @ 2010-05-07 13:02 UTC (permalink / raw)
To: Jan Beulich; +Cc: xen-devel@lists.xensource.com
On 07/05/2010 13:36, "Jan Beulich" <JBeulich@novell.com> wrote:
> Keir,
>
> isn't there a problem after the change to handle tasklets in idle vcpus
> in that {default,acpi_processor}_idle() will put the vcpu to sleep with
> boosted priority still in place, hence preventing it from being tickled
> and/or needlessly tickling other CPUs?
See the comment above tasklet_list definition in tasklet.c: we always run
through the scheduler when tasklets are added/removed. That is explicitly to
get the idle thread's priority set correctly.
I think this could be handled better though, and also in the current
approach I actually still probably don't have enough raise_softirq() calls.
:-) I will take another look and see if I can make things more obvious and
robust.
Thanks,
Keir
> Jan
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: bad interaction between boosted idle vcpus and csched's tickling?
2010-05-07 12:36 bad interaction between boosted idle vcpus and csched's tickling? Jan Beulich
2010-05-07 13:02 ` Keir Fraser
@ 2010-05-11 10:14 ` Keir Fraser
1 sibling, 0 replies; 3+ messages in thread
From: Keir Fraser @ 2010-05-11 10:14 UTC (permalink / raw)
To: Jan Beulich; +Cc: xen-devel@lists.xensource.com
On 07/05/2010 13:36, "Jan Beulich" <JBeulich@novell.com> wrote:
> Keir,
>
> isn't there a problem after the change to handle tasklets in idle vcpus
> in that {default,acpi_processor}_idle() will put the vcpu to sleep with
> boosted priority still in place, hence preventing it from being tickled
> and/or needlessly tickling other CPUs?
Should be resolved by xen-unstable:21344.
-- Keir
^ permalink raw reply [flat|nested] 3+ messages in thread
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