linux-kernel - Too many poll_idle cpu calls in kernel 3.2 rc-series

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Date:	Sun, 27 Nov 2011 21:13:28 +0100 (CET)
From:	"Nicolas Kalkhof" <nkalkhof@....de>
To:	linux-kernel@...r.kernel.org
Subject: Too many poll_idle cpu calls in kernel 3.2 rc-series

the kernel v3.2 series shows excessive poll_idle calls during system idle phases causing the cpu
(mobile i7 2620M) to heat up and draw additional 10% more power.  All kernel versions between
3.2-rc1 and 3.2-rc3 are affected. Perf Top and Powertop both show the same issue.
I've posted a similar bug report before: http://marc.info/?l=linux-kernel&m=132164909313594&w=2
and used perf top -U to verify the poll_idle calls as requested.

dmesg and kernel .config attached.

Could someone please confirm this issue?

Thanks and Regards
Nic

perf top -U shows:
Events: 30K cycles
 97.88%  [kernel]   [k] poll_idle
  0.17%  [kernel]   [k] sdhci_irq
  0.08%  [kernel]   [k] unix_poll
  0.06%  [kernel]   [k] _raw_spin_lock_irqsave
  0.06%  [kernel]   [k] page_fault
  0.05%  [kernel]   [k] fget_light
  0.05%  [kernel]   [k] format_decode
  0.04%  [kernel]   [k] kmem_cache_alloc
  0.04%  [kernel]   [k] clear_page
  0.04%  [kernel]   [k] _raw_spin_unlock_irqrestore
  0.03%  [kernel]   [k] do_select
  0.03%  [kernel]   [k] seq_printf
  0.03%  [kernel]   [k] vfs_read
  0.03%  [kernel]   [k] _raw_spin_lock
  0.03%  [kernel]   [k] vsnprintf
  0.03%  [kernel]   [k] number.clone.1
  0.03%  [kernel]   [k] fput

Powertop shows:
n                Avg residency       P-states (frequencies)
C0 (cpu running)        ( 5.4%)       Turbo Mode     1.5%
polling           1.8ms (94.6%)         2.71 Ghz     0.1%
C1 mwait          0.0ms ( 0.0%)         2.21 Ghz     0.1%
C2 mwait          0.0ms ( 0.0%)         1400 Mhz     0.1%
C3 mwait          0.0ms ( 0.0%)          800 Mhz    98.2%
C4 mwait          0.0ms ( 0.0%)
Wakeups-from-idle per second : 529.4    interval: 5.0s



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Download attachment "dmesg.log" of type "application/octet-stream" (38915 bytes)

Download attachment ".config" of type "application/octet-stream" (63214 bytes)