[PATCH][2/2] ondemand governor store the idle ticks for all cpus

[PATCH][2/2] ondemand governor store the idle ticks for all cpus

[Eric Piel]

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Hello,

While doing the previous cleanup I noticed that until now only the 
prev_cpu_idle_up of the current CPU would be stored to 
prev_cpu_idle_down. In case of several associated CPUs, all the 
measurement is based on looking every CPU statistic. Therefore it is 
necessary to also save the prev_cpu_idle_up of the other associated CPUs.

This patch fixes this by adding a small loop. As the previous patch, 
it's against 2.6.11 and only tested on a monoprocessor PC.

Eric

PS: I couldn't find any documentation concerning the implementation of 
several CPUs with a frequency attached, is there any reference?

--
Ondemand governor did not store prev_cpu_idle_up into prev_cpu_idle_down 
for other CPUs than the current CPU.

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

[-- Attachment #2: ondemand-save-idle-up-for-all-cpu-2.6.11.patch --]
[-- Type: text/x-patch, Size: 587 bytes --]

--- linux-2.6.11/drivers/cpufreq/cpufreq_ondemand.c.clean2	2005-03-06 19:04:12.000000000 +0100
+++ linux-2.6.11/drivers/cpufreq/cpufreq_ondemand.c	2005-03-06 19:09:52.000000000 +0100
@@ -277,7 +277,12 @@
 		__cpufreq_driver_target(policy, policy->max, 
 			CPUFREQ_RELATION_H);
 		down_skip[cpu] = 0;
-		this_dbs_info->prev_cpu_idle_down = this_dbs_info->prev_cpu_idle_up;
+		for_each_cpu_mask(j, policy->cpus) {
+			struct cpu_dbs_info_s *j_dbs_info;
+
+			j_dbs_info = &per_cpu(cpu_dbs_info, j);
+			j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
+		}
 		return;
 	}
 

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RE: [PATCH][2/2] ondemand governor store the idle ticks for all cpus

[Pallipadi, Venkatesh]

>-----Original Message-----
>From: Eric Piel [mailto:Eric.Piel@tremplin-utc.net] 
>Sent: Sunday, March 06, 2005 10:52 AM
>To: Pallipadi, Venkatesh
>
>This patch fixes this by adding a small loop. As the previous patch, 
>it's against 2.6.11 and only tested on a monoprocessor PC.
>

Good catch. 
Dave/Dominik: please apply these two patches. 
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>

>
>PS: I couldn't find any documentation concerning the implementation of 
>several CPUs with a frequency attached, is there any reference?

Only documentation for several CPUs with freq attached:
(From patch comments)
The following patch makes ondemand governor aware of policy->cpus.

policy->cpus mask lets multiple cpu use the same policy (useful where
cpus
share the frequency state), a recent change in cpufreq core.

Now ondemand governor looks at all cpus in policy->cpus and takes its
frequency increase/decrease decisions based on most lightly loaded cpu
in
the group. This patch will not affect systems where policy->cpus contain
only one cpu.

Thanks,
Venki