From mboxrd@z Thu Jan  1 00:00:00 1970
From: Laszlo Ersek <lersek@redhat.com>
Subject: Re: [PATCH] remove blocked time accounting from xen
	"clockchip"
Date: Thu, 20 Oct 2011 17:02:41 +0200
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Cc: xen-devel@lists.xensource.com, Joe Jin <joe.jin@oracle.com>, Zhenzhong Duan <zhenzhong.duan@oracle.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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On 10/20/11 16:35, Laszlo Ersek wrote:

> I'm convinced the patch is correct, and only the commit message might
> need a small fix (mentioning cpu_idle()).

I forgot to say that I also added counters to xen_timer_interrupt(), 
account_idle_ticks() (called from cpu_idle()), and the idle time branch 
of account_process_tick(). (The last one is reached from 
xen_timer_interrupt() via event_handler == &tick_nohz_handler, after 
highres=off was passed). When the VM was left alone, they were 
increasing in strict lock-step.

account_idle_time()

   <- account_idle_ticks()
     <- tick_nohz_restart_sched_tick()
       <- cpu_idle()

   <- account_process_tick()
     <- update_process_times()
       <- tick_nohz_handler() [highres=off]
         <- xen_timer_interrupt()

       <- (tick_periodic())
       <- (tick_sched_timer())

The timer interrupt appears to kick cpu_idle(), and the latter accounts 
for the time spent idly.

Laszlo