Re: [PATCH] remove blocked time accounting from xen "clockchip"

[Laszlo Ersek <lersek@redhat.com>]

On 10/19/11 09:51, Jan Beulich wrote:
>>>> On 18.10.11 at 22:42, Laszlo Ersek<lersek@redhat.com>  wrote:
>> ... because the "clock_event_device framework" already accounts for idle
>> time through the "event_handler" function pointer in
>> xen_timer_interrupt().
>
> As event_handler is being checked to be non-zero, shouldn't the
> code you remove simply become conditional (upon event_handler
> being zero)?

I think that wouldn't be hard to implement, but I'm afraid the paragraph 
you quoted from my proposed commit message could be wrong -- perhaps 
it's not the event_handler callback that cranks the idle time counter. 
Please see

https://bugzilla.redhat.com/show_bug.cgi?id=624756#c26

In short,

(a) idle time is increased in cpu_idle(), which seems to be running as a 
standalone kernel thread;

(b) the event_handler I found invoked from xen_timer_interrupt() is 
hrtimer_interrupt();

(c) I couldn't figure out if cpu_idle() keeps waking up "on its own", or 
if it needs periodic kicks from hrtimer_interrupt() (executed by some 
other thread).

Thank you
Laszlo