linux-stable.git/drivers/cpuidle, branch linux-2.6.33.y

cpuidle: menu: fixed wrapping timers at 4.294 seconds

2011-06-23T22:28:37+00:00

commit 7467571f4480b273007517b26297c07154c73924 upstream.

Cpuidle menu governor is using u32 as a temporary datatype for storing
nanosecond values which wrap around at 4.294 seconds. This causes errors
in predicted sleep times resulting in higher than should be C state
selection and increased power consumption. This also breaks cpuidle
state residency statistics.

Signed-off-by: Tero Kristo 
Signed-off-by: Len Brown 
Signed-off-by: Greg Kroah-Hartman

cpuidle: Fix incorrect optimization

2010-05-12T22:03:10+00:00

commit 1c6fe0364fa7bf28248488753ee0afb6b759cd04 upstream.

commit 672917dcc78 ("cpuidle: menu governor: reduce latency on exit")
added an optimization, where the analysis on the past idle period moved
from the end of idle, to the beginning of the new idle.

Unfortunately, this optimization had a bug where it zeroed one key
variable for new use, that is needed for the analysis.  The fix is
simple, zero the variable after doing the work from the previous idle.

During the audit of the code that found this issue, another issue was
also found; the ->measured_us data structure member is never set, a
local variable is always used instead.

Signed-off-by: Arjan van de Ven 
Cc: Corrado Zoccolo 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

drivers/cpuidle/governors/menu.c: fix undefined reference to `__udivdi3'

2010-01-11T17:34:07+00:00

menu: use proper 64 bit math

The new menu governor is incorrectly doing a 64 bit divide.  Compile
tested only

Signed-off-by: Stephen Hemminger 
Cc: Arjan van de Ven 
Cc: Len Brown 
Cc: Venkatesh Pallipadi 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

drivers/cpuidle: Move dereference after NULL test

2009-12-15T16:53:25+00:00

It does not seem possible that ldev can be NULL, so drop the unnecessary
test.  If ldev can somehow be NULL, then the initialization of last_idx
should be moved below the test.

A simplified version of the semantic match that detects this problem is as
follows (http://coccinelle.lip6.fr/):

// 
@match exists@
expression x, E;
identifier fld;
@@

* x->fld
  ... when != \(x = E\|&x\)
* x == NULL
// 

Signed-off-by: Julia Lawall 
Acked-by: Arjan van de Ven 
Cc: Ingo Molnar 
Cc: Venkatesh Pallipadi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tree-wide: fix typos "aquire" -> "acquire", "cumsumed" -> "consumed"

2009-11-09T08:40:57+00:00

This patch was generated by

	git grep -E -i -l '[Aa]quire' | xargs -r perl -p -i -e 's/([Aa])quire/$1cquire/'

and the cumsumed was found by checking the diff for aquire.

Signed-off-by: Uwe Kleine-König 
Signed-off-by: Jiri Kosina

cpuidle: always return with interrupts enabled

2009-10-29T14:39:31+00:00

In the case where cpuidle_idle_call() returns before changing state due to
a need_resched(), it was returning with IRQs disabled.

The idle path assumes that the platform specific idle code returns with
interrupts enabled (although this too is undocumented AFAICT) and on ARM
we have a WARN_ON(!(irqs_disabled()) when returning from the idle loop, so
the user-visible effects were only a warning since interrupts were
eventually re-enabled later.

On x86, this same problem exists, but there is no WARN_ON() to detect it.
As on ARM, the interrupts are eventually re-enabled, so I'm not sure of
any actual bugs triggered by this.  It's primarily a
correctness/consistency fix.

This patch ensures IRQs are (re)enabled before returning.

Reported-by: Hemanth V 
Signed-off-by: Kevin Hilman 
Cc: Arjan van de Ven 
Cc: Len Brown 
Cc: Venkatesh Pallipadi 
Cc: Ingo Molnar 
Cc: "Rafael J. Wysocki" 
Tested-by: Martin Michlmayr 
Cc: 		[2.6.31.x]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

cpuidle: menu governor: reduce latency on exit

2009-09-22T14:17:45+00:00

Move the state residency accounting and statistics computation off the hot
exit path.

On exit, the need to recompute statistics is recorded, and new statistics
will be computed when menu_select is called again.

The expected effect is to reduce processor wakeup latency from sleep
(C-states).  We are speaking of few hundreds of cycles reduction out of a
several microseconds latency (determined by the hardware transition), so
it is difficult to measure.

Signed-off-by: Corrado Zoccolo 
Cc: Venkatesh Pallipadi 
Cc: Len Brown 
Cc: Adam Belay 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

cpuidle: fix the menu governor to boost IO performance

2009-09-22T14:17:45+00:00

Fix the menu idle governor which balances power savings, energy efficiency
and performance impact.

The reason for a reworked governor is that there have been serious
performance issues reported with the existing code on Nehalem server
systems.

To show this I'm sure Andrew wants to see benchmark results:
(benchmark is "fio", "no cstates" is using "idle=poll")

		no cstates	current linux	new algorithm
1 disk		107 Mb/s	85 Mb/s		105 Mb/s
2 disks		215 Mb/s	123 Mb/s	209 Mb/s
12 disks	590 Mb/s	320 Mb/s	585 Mb/s

In various power benchmark measurements, no degredation was found by our
measurement&diagnostics team.  Obviously a small percentage more power was
used in the "fio" benchmark, due to the much higher performance.

While it would be a novel idea to describe the new algorithm in this
commit message, I cheaped out and described it in comments in the code
instead.

[changes since first post: spelling fixes from akpm, review feedback,
folded menu-tng into menu.c]

Signed-off-by: Arjan van de Ven 
Cc: Venkatesh Pallipadi 
Cc: Len Brown 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Yanmin Zhang 
Acked-by: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tracing, x86, cpuidle: Move the end point of a C state in the power tracer

2009-09-19T16:57:52+00:00

The "end of a C state" trace point currently happens before
the code runs that corrects the TSC for having stopped during idle.

The result of this is that the timestamp of the end-of-C-state event
is garbage on cpus where the TSC stops during idle.

This patch moves the end point of the C state to after the timekeeping
engine of the kernel has been corrected.

Signed-off-by: Arjan van de Ven 
Cc: Len Brown 
Cc: fweisbec@gmail.com
Cc: peterz@infradead.org
Cc: Paul Mackerras 
LKML-Reference: <20090919133533.139c2a46@infradead.org>
Signed-off-by: Ingo Molnar

cpuidle: Add decaying history logic to menu idle predictor

2008-12-30T23:48:01+00:00

Add decaying history of predicted idle time, instead of using the last early
wakeup. This logic helps menu governor do better job of predicting idle time.

With this change, we also measured noticable (~8%) power savings on
a DP server system with CPUs supporting deep C states, when system
was lightly loaded. There was no change to power or perf on other load
conditions.

Signed-off-by: Venkatesh Pallipadi 
Signed-off-by: Len Brown