2007-12-25 04:37:20

by Denys Fedoryschenko

[permalink] [raw]
Subject: nmi_watchdog killing tickless feature

Hi

Please CC me on reply, i am not subscribed to list.

I did small test, and notice that if nmi_watchdog is enabled
mpstat 1

06:11:00 CPU %user %nice %sys %iowait %irq %soft %steal
%idle intr/s
06:11:01 all 0.00 0.00 0.00 0.00 0.00 0.00 0.00
100.00 993.07
06:11:02 all 0.00 0.00 0.00 0.00 0.00 0.00 0.00
100.00 1007.00
06:11:03 all 0.00 0.00 0.00 0.00 0.00 0.00 0.00
100.00 1005.00

if disabled
06:13:52 CPU %user %nice %sys %iowait %irq %soft %steal
%idle intr/s
06:13:53 all 0.00 0.00 0.00 0.00 0.00 0.00 0.00
100.00 1.00
06:13:54 all 0.00 0.00 0.00 0.00 0.00 0.00 0.00
100.00 9.00
06:13:55 all 0.00 0.00 0.00 0.00 0.00 0.00 0.00
100.00 4.00
06:13:56 all 0.00 0.00 0.00 0.00 0.00 0.00 0.00
100.00 2.00
06:13:57 all 0.00 0.00 0.00 0.00 0.00 0.00 0.00
100.00 2.00

The difference is huge, probably in power consumption too. Kernel is
relatively standard (2.6.24-rc6-git1), if required i can attach .config
If it is not bug, probably good to document, that it is killing powersaving
features?

--
Denys Fedoryshchenko
Technical Manager
Virtual ISP S.A.L.