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authorVenkatesh Pallipadi <venki@google.com>2010-10-04 17:03:22 -0700
committerIngo Molnar <mingo@elte.hu>2010-10-18 20:52:27 +0200
commitaa483808516ca5cacfa0e5849691f64fec25828e (patch)
tree38a1d9f1cb1157bd68dc2475447bacbb4b63c64a /kernel/sched_fair.c
parent305e6835e05513406fa12820e40e4a8ecb63743c (diff)
sched: Remove irq time from available CPU power
The idea was suggested by Peter Zijlstra here: http://marc.info/?l=linux-kernel&m=127476934517534&w=2 irq time is technically not available to the tasks running on the CPU. This patch removes irq time from CPU power piggybacking on sched_rt_avg_update(). Tested this by keeping CPU X busy with a network intensive task having 75% oa a single CPU irq processing (hard+soft) on a 4-way system. And start seven cycle soakers on the system. Without this change, there will be two tasks on each CPU. With this change, there is a single task on irq busy CPU X and remaining 7 tasks are spread around among other 3 CPUs. Signed-off-by: Venkatesh Pallipadi <venki@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1286237003-12406-8-git-send-email-venki@google.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_fair.c')
-rw-r--r--kernel/sched_fair.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index c358d4081b81..74cccfae87a8 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -2275,7 +2275,13 @@ unsigned long scale_rt_power(int cpu)
u64 total, available;
total = sched_avg_period() + (rq->clock - rq->age_stamp);
- available = total - rq->rt_avg;
+
+ if (unlikely(total < rq->rt_avg)) {
+ /* Ensures that power won't end up being negative */
+ available = 0;
+ } else {
+ available = total - rq->rt_avg;
+ }
if (unlikely((s64)total < SCHED_LOAD_SCALE))
total = SCHED_LOAD_SCALE;