[Bug 4379] Default sampling rates for ondemand governor are too high on a amd64

[Bug 4379] Default sampling rates for ondemand governor are too high on a amd64

[bugme-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=4379





------- Additional Comments From linux@brodo.de  2005-11-15 13:53 -------
Is this problem still present in 2.6.14?

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Re: [Bug 4379] Default sampling rates for ondemand governor are too high on a amd64

[Eric Piel]

[-- Attachment #1: Type: text/plain, Size: 883 bytes --]

15.11.2005 22:59, bugme-daemon@bugzilla.kernel.org wrote/a écrit:
> http://bugzilla.kernel.org/show_bug.cgi?id=4379
> 
> 
> 
> 
> 
> ------- Additional Comments From linux@brodo.de  2005-11-15 13:53 -------
> Is this problem still present in 2.6.14?
> 
I think so.

Well, I've got a patch that should fix it. It make the polling frequency 
10 times faster than it used to be. This is valid _only_ for kernel >= 
2.6.15-rc1 because there is now a check to avoid polling too fast. I've 
tested it here, on my pentium III it works.

Venki, do you see any problem with this patch?

Eric

-- 
From: Eric Piel <eric.piel@tremplin-utc.net>

Make the polling frequency 10 times faster than it used to be, now that 
there is a check to avoid too high freqencies. Solve problems with 
hardwares which have a long transition latency.

Signed-off-by: Eric Piel <eric.piel@tremplin-utc.net>
-- 

[-- Attachment #2: cpufreq-ondemand-more-frequent-polling-2.6.15-rc1.patch --]
[-- Type: text/x-patch, Size: 1074 bytes --]

--- linux-2.6.14/drivers/cpufreq/cpufreq_ondemand.c.bak	2005-11-16 08:35:14.000000000 +0100
+++ linux-2.6.14/drivers/cpufreq/cpufreq_ondemand.c	2005-11-16 08:36:57.000000000 +0100
@@ -39,7 +39,7 @@
 
 /* 
  * The polling frequency of this governor depends on the capability of 
- * the processor. Default polling frequency is 1000 times the transition
+ * the processor. Default polling frequency is 100 times the transition
  * latency of the processor. The governor will work on any processor with 
  * transition latency <= 10mS, using appropriate sampling 
  * rate.
@@ -53,7 +53,7 @@ static unsigned int 				def_sampling_rat
 #define MIN_STAT_SAMPLING_RATE			(MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
 #define MIN_SAMPLING_RATE			(def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
 #define MAX_SAMPLING_RATE			(500 * def_sampling_rate)
-#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER	(1000)
+#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER	(100)
 #define DEF_SAMPLING_DOWN_FACTOR		(1)
 #define MAX_SAMPLING_DOWN_FACTOR		(10)
 #define TRANSITION_LATENCY_LIMIT		(10 * 1000)

[-- Attachment #3: Type: text/plain, Size: 147 bytes --]

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[Bug 4379] Default sampling rates for ondemand governor are too high on a amd64

[bugme-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=4379





------- Additional Comments From piel@lifl.fr  2006-02-05 02:46 -------
Created an attachment (id=7248)
 --> (http://bugzilla.kernel.org/attachment.cgi?id=7248&action=view)
Reduce the default sampling rate to check more often

Hello,

Could you try the attached patch against 2.6.15 or 2.6.16 and confirm it solves
your problem ? As there is now a check to avoid polling too fast, it should not
be dangerous to check more often.

Eric

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[Bug 4379] Default sampling rates for ondemand governor are too high on a amd64

[bugme-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=4379

sigra@home.se changed:

           What    |Removed                     |Added
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[Bug 4379] Default sampling rates for ondemand governor are too high on a amd64

[bugme-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=4379


protasnb@gmail.com changed:

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------- Comment #5 from protasnb@gmail.com  2007-11-17 23:02 -------
Eric, what about commit df8b59be0976c56820453730078bef99a8d1dbda, "Avoid the
ondemand cpufreq governor to use a too high frequency for stats" - does it
resolve this problem?
Thanks.


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[Bug 4379] Default sampling rates for ondemand governor are too high on a amd64

[bugme-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=4379





------- Comment #6 from piel@lifl.fr  2007-11-19 05:17 -------
(Sorry for answering late, I haven't received directly any email, just saw the
message on the mailing list.)

What I was talking about in comment #4 was this commit. It's to keep the the
frequency low enough compared to the scheduler. The attached patch, on the
contrary, _increases_ the frequency. 

Unfortunately Gunther hasn't confirm this patch helps with his problem.
However, now the sampling down is done as often as the sampling up so it should
be less problematic anyway. 1000 is a very conservative value but nowadays,
with the great hunt for reducing the wakeups that can probably be considered
fine. It would be nice if Gunther could confirm the behavior is currently
better (slow down happens fast enough)...


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[Bug 4379] Default sampling rates for ondemand governor are too high on a amd64

[bugme-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=4379


kernel-io@fionn.de changed:

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------- Comment #7 from kernel-io@fionn.de  2008-05-14 06:39 -------
This problem has has been HUGELY WORSENED in kernel 2.6.25 since someone
apparently opted to RAISE the minimum sampling rate to whopping 2500000.
Even with the minimum settings, the ondemand governor now acts so sluggish that
it is basically unusuable. I had to switch to userspace governor and powernowd
which I consider a significant step backwards.

Would someone with sufficient rights please add 2.6.25 to the kernel version in
bugzilla? Otherwise I'll open a new bug for that version soon.


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[Bug 4379] Default sampling rates for ondemand governor are too high on a amd64

[bugme-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=4379





------- Comment #8 from kernel-io@fionn.de  2008-05-14 06:44 -------
argh argh argh. sorry. my last comment does NOT apply to the ondemand but to
conservative governor. I'll open a separate bug for that

Sorry again. tried not to duplicate anything but should have read better


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[Bug 4379] Default sampling rates for ondemand governor are too high on a amd64

[bugme-daemon]

http://bugzilla.kernel.org/show_bug.cgi?id=4379


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[Bug 4379] Default sampling rates for ondemand governor are too high on a amd64

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trenn@suse.de changed:

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