Jeremy Fitzhardinge wrote:
On 10/10/2011 08:53 AM, Konrad Rzeszutek Wilk wrote:
On Wed, Oct 05, 2011 at 10:11:58PM -0700, Zhenzhong Duan wrote:
Run below test on xen pvm.
# x=$(cat /proc/stat | grep cpu0 | awk '{print $5}') && sleep 60 \
&& y=$(cat /proc/stat | grep cpu0 | awk '{print $5}') \
&& echo -e "X:$x\nY:$y\nIDLE:" $(echo "scale=3; ($y-$x)/6000*100" | bc)
@ X:58562301
@ Y:58574282
@ IDLE: 199.600
Normal idle percent should be around 100%.
xen_timer_interrupt called account_idle_ticks to account hypervisor stolen idle ticks
but these ticks will be accounted again when idle ticks restarted.
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
Signed-off-by: Joe Jin <joe.jin@xxxxxxxxxx>
Please in the future also CC the maintainers (you can get that using
the scripts/get_maintainer.pl).
Jeremy, any thoughts?
Does this affect the accounting of stolen ticks? If it does, that's not
necessarily a showstopper for this patch, but we'll need to do some more
thinking about it. Certainly, accurate accounting for idleness is
important.
J
Thanks Konrad for point out that.
In Original kernel, tick_nohz_restart_sched_tick and
do_stolen_accounting both called account_idle_ticks.
For a idle pvm, idle/iowait maybe doubled apparently.
Normally Y-X should get close to 6000 in idle system, but in my test
it's 11981.
But I am still not sure if patch has any impact to other part. Thanks
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 163b467..5dcbc91 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -151,7 +151,6 @@ static void do_stolen_accounting(void)
ticks = iter_div_u64_rem(blocked, NS_PER_TICK, &blocked);
__this_cpu_write(xen_residual_blocked, blocked);
- account_idle_ticks(ticks);
}
/* Get the TSC speed from Xen */
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--
Regards
zhenzhong
--
Oracle Building, No.24 Building, Zhongguancun Software Park
Haidian District, Beijing 100193, China
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