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sched: Fix capacity calculations for SMT4

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Handle cpu capacity being reported as 0 on cores with more number of
hardware threads. For example on a Power7 core with 4 hardware
threads, core power is 1177 and thus power of each hardware thread is
1177/4 = 294. This low power can lead to capacity for each hardware
thread being calculated as 0, which leads to tasks bouncing within the
core madly!

Fix this by reporting capacity for hardware threads as 1, provided
their power is not scaled down significantly because of frequency
scaling or real-time tasks usage of cpu.

Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arjan van de Ven <arjan@linux.intel.com>
LKML-Reference: <20100608045702.21D03CC895@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Srivatsa Vaddagiri
2010-06-08 14:57:02 +10:00
committed by Ingo Molnar
parent 83cd4fe27a
commit 9d5efe05eb
2 changed files with 44 additions and 11 deletions
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2
include/linux/sched.h
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@ -857,7 +857,7 @@ struct sched_group {
* CPU power of this group, SCHED_LOAD_SCALE being max power for a
* single CPU.
*/
unsigned int cpu_power;
unsigned int cpu_power, cpu_power_orig;
/*
* The CPUs this group covers.