Messages in this thread | | | Date | Thu, 24 Mar 2016 21:18:53 +0800 | From | Jisheng Zhang <> | Subject | Re: [PATCH 0/2] arm64: cpuidle: make arm_cpuidle_suspend() more efficient |
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Hi Will,
On Thu, 24 Mar 2016 11:15:07 +0000 Will Deacon wrote:
> On Thu, Mar 24, 2016 at 01:08:48PM +0800, Jisheng Zhang wrote: > > This series is to improve the arm_cpuidle_suspend() a bit by removing/moving > > out checks from this hot path. > > > > Jisheng Zhang (2): > > arm64: cpuidle: remove cpu_ops check from arm_cpuidle_suspend() > > arm64: cpuidle: make arm_cpuidle_suspend() a bit more efficient > > > > arch/arm64/kernel/cpuidle.c | 9 ++------- > > 1 file changed, 2 insertions(+), 7 deletions(-) > > These look fine to me, but do you have any rough numbers showing what > sort of improvement we get from this change?
Good question. Here it is:
I measured the 4096 * time from arm_cpuidle_suspend entry point to the cpu_psci_cpu_suspend entry point. HW platform is Marvell BG4CT STB board.
1. only one shell, no other process, hot-unplug secondary cpus, execute the following cmd
while true do sleep 0.2 done
before the patch: 1581220ns
after the patch: 1579630ns
reduced by 0.1%
2. only one shell, no other process, hot-unplug secondary cpus, execute the following cmd
while true do md5sum /tmp/testfile sleep 0.2 done
NOTE the testfile size should be larger than L1+L2 cache size
before the patch: 1961960ns after the patch: 1912500ns
reduced by 2.5%
So the more complex the system load, the bigger the improvement.
Thanks, Jisheng
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