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Date: Mon, 27 Sep 2010 17:29:55 -0700
From: Nikhil Rao <ncrao@...gle.com>
To: Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
Mike Galbraith <efault@....de>
Cc: Venkatesh Pallipadi <venki@...gle.com>,
linux-kernel@...r.kernel.org, Nikhil Rao <ncrao@...gle.com>
Subject: [PATCH 0/3][RFC] Improve load balancing when tasks have large weight differential
Hi all,
I have attached a series of patches that improve load balancing when there is a
large weight differential between tasks. These patches are based off the
feedback Peter Zijlstra gave in an earlier post (see http://thread.gmane.org/gmane.linux.kernel/1015966).
They can be applied to v2.6.36-rc5 or -tip without conflicts.
Tested with the following setup.
- Test machine is a 16 cpu box (quad-socket, quad-core).
- Baseline is v2.6.36-rc5 kernel
We spawn 16 SCHED_IDLE soaker threads and one SCHED_NORMAL task. On the
baseline kernel, the machine has ~18% idle time. With these patches applied on
top of baseline, idle time drops to 0%.
v2.6.36-rc5
04:58:46 PM CPU %user %nice %sys %iowait %irq %soft %steal %idle intr/s
04:58:47 PM all 81.47 0.00 0.25 0.00 0.00 0.00 0.00 18.28 13796.00
04:58:48 PM all 81.20 0.00 0.25 0.00 0.00 0.00 0.00 18.55 13816.00
04:58:49 PM all 80.93 0.19 0.25 0.00 0.00 0.06 0.00 18.57 13965.00
04:58:50 PM all 81.40 0.00 0.25 0.00 0.00 0.00 0.00 18.35 13837.37
04:58:51 PM all 81.19 0.00 0.31 0.00 0.00 0.00 0.00 18.50 13592.08
04:58:52 PM all 81.25 0.00 0.25 0.00 0.00 0.00 0.00 18.50 13721.00
04:58:53 PM all 81.19 0.00 0.25 0.00 0.00 0.00 0.00 18.56 13764.00
04:58:54 PM all 81.25 0.00 0.25 0.00 0.00 0.00 0.00 18.50 13841.41
04:58:55 PM all 80.30 0.00 1.19 0.00 0.00 0.00 0.00 18.51 14989.11
04:58:56 PM all 80.77 0.00 0.50 0.00 0.00 0.00 0.00 18.73 13964.65
Average: all 81.09 0.02 0.37 0.00 0.00 0.01 0.00 18.51 13929.53
v2.6.36-rc5 + patches
05:00:06 PM CPU %user %nice %sys %iowait %irq %soft %steal %idle intr/s
05:00:07 PM all 99.94 0.00 0.06 0.00 0.00 0.00 0.00 0.00 16364.00
05:00:08 PM all 99.81 0.06 0.12 0.00 0.00 0.00 0.00 0.00 16348.00
05:00:09 PM all 99.94 0.00 0.06 0.00 0.00 0.00 0.00 0.00 16330.00
05:00:10 PM all 99.94 0.00 0.06 0.00 0.00 0.00 0.00 0.00 16317.00
05:00:11 PM all 99.88 0.06 0.06 0.00 0.00 0.00 0.00 0.00 16327.00
05:00:12 PM all 99.94 0.00 0.06 0.00 0.00 0.00 0.00 0.00 16323.00
05:00:13 PM all 99.88 0.00 0.12 0.00 0.00 0.00 0.00 0.00 16323.00
05:00:14 PM all 99.94 0.00 0.06 0.00 0.00 0.00 0.00 0.00 16321.00
05:00:15 PM all 99.63 0.06 0.25 0.00 0.00 0.06 0.00 0.00 16354.00
05:00:16 PM all 99.62 0.00 0.38 0.00 0.00 0.00 0.00 0.00 19059.60
Average: all 99.85 0.02 0.13 0.00 0.00 0.01 0.00 0.00 16604.20
Comments, feedback welcome.
-Thanks,
Nikhil
Nikhil Rao (3):
sched: set group_imb only a task can be pulled from the busiest cpu
sched: drop group_capacity to 1 only if remote group has no running
tasks
sched: do not consider SCHED_IDLE tasks to be cache hot
kernel/sched.c | 3 +++
kernel/sched_fair.c | 12 ++++++++----
2 files changed, 11 insertions(+), 4 deletions(-)
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