On 19 Aug 2015 17:58, "Jon Medhurst (Tixy)" tixy@linaro.org wrote:
Adding Patrick Bellasi to the 'to' list as he's been working on HMP with Chris Redpath....
On Wed, 2015-08-19 at 05:18 +0000, Rahul Khandelwal (Rahul Khandelwal)
wrote:
Dear All,
Please consider the patch, It is related to HMP force up migration. It
will avoid sending of unnecessary interrupts to CPUs of faster domain hence increase performance.
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From 2d48749ac30a2c0a2ef77132f303d69605c3dd3f Mon Sep 17 00:00:00 2001 From: rahulkhandelwal rahul.khandelwal@spreadtrum.com Date: Fri, 14 Aug 2015 16:36:17 +0800 Subject: [PATCH 1/1] HMP: Do not send IPI if core already waked up
It is possible that we are sending IPI to a cpu in faster domain which is already waked up by other CPU in smaller domain.
HMP select the idle CPU using hmp_domain_min_load. Based on that HMP send
IPI
to the idle cpu in faster domain. There could be some latency by the core
to
wake up and set wake_for_idle_pull = 0. Next smaller cpu again check for idle CPU in faster domain and send IPI to already waked up CPU.
For example: In Octacore system, 0-3 are slower CPUs and 4-7 are faster
CPUs.
CPU0 and CPU1 has heavy tasks and CPU4 is idle. CPU0 execute hmp_force_up_migration find CPU4 as idle, it send IPI to CPU4 and return. After that CPU1 got the chance to run hmp_force_up_migration, it again find CPU4 as idle, send IPI to CPU4, which is not required.
Signed-off-by: rahulkhandelwal rahul.khandelwal@spreadtrum.com
kernel/sched/fair.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1baf641..388836c 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7200,6 +7200,11 @@ static void hmp_force_up_migration(int this_cpu) } p = task_of(curr); if (hmp_up_migration(cpu, &target_cpu,
curr)) {
if
(cpu_rq(target_cpu)->wake_for_idle_pull == 1) {
raw_spin_unlock_irqrestore(&target->lock, flags);
spin_unlock(&hmp_force_migration);
return;}
cpu_rq(target_cpu)->wake_for_idle_pull = 1;
raw_spin_unlock_irqrestore(&target->lock, flags);
spin_unlock(&hmp_force_migration);
Can you please share the actual performance numbers gained by this patch?
-- 1.7.9.5
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