diff options
author | Jisheng Zhang <jszhang@marvell.com> | 2016-03-25 11:08:55 +0800 |
---|---|---|
committer | Will Deacon <will.deacon@arm.com> | 2016-04-13 14:49:23 +0100 |
commit | b5fda7ed5c63297d0f43e608b455d82ceabdebf0 (patch) | |
tree | dd41c52a99da577a06101f4917a11dbd90455014 /arch/arm64/kernel/cpuidle.c | |
parent | 7d7b4ae418728916456c6fd03a97ef35345ff30d (diff) | |
download | linux-stable-b5fda7ed5c63297d0f43e608b455d82ceabdebf0.tar.gz linux-stable-b5fda7ed5c63297d0f43e608b455d82ceabdebf0.tar.bz2 linux-stable-b5fda7ed5c63297d0f43e608b455d82ceabdebf0.zip |
arm64: cpuidle: make arm_cpuidle_suspend() a bit more efficient
Currently, we check two pointers: cpu_ops and cpu_suspend on every idle
state entry. These pointers check can be avoided:
If cpu_ops has not been registered, arm_cpuidle_init() will return
-EOPNOTSUPP, so arm_cpuidle_suspend() will never have chance to
run. In other word, the cpu_ops check can be avoid.
Similarly, the cpu_suspend check could be avoided in this hot path by
moving it into arm_cpuidle_init().
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.
Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel/cpuidle.c')
-rw-r--r-- | arch/arm64/kernel/cpuidle.c | 9 |
1 files changed, 2 insertions, 7 deletions
diff --git a/arch/arm64/kernel/cpuidle.c b/arch/arm64/kernel/cpuidle.c index 9047cab68fd3..e11857fce05f 100644 --- a/arch/arm64/kernel/cpuidle.c +++ b/arch/arm64/kernel/cpuidle.c @@ -19,7 +19,8 @@ int __init arm_cpuidle_init(unsigned int cpu) { int ret = -EOPNOTSUPP; - if (cpu_ops[cpu] && cpu_ops[cpu]->cpu_init_idle) + if (cpu_ops[cpu] && cpu_ops[cpu]->cpu_suspend && + cpu_ops[cpu]->cpu_init_idle) ret = cpu_ops[cpu]->cpu_init_idle(cpu); return ret; @@ -36,11 +37,5 @@ int arm_cpuidle_suspend(int index) { int cpu = smp_processor_id(); - /* - * If cpu_ops have not been registered or suspend - * has not been initialized, cpu_suspend call fails early. - */ - if (!cpu_ops[cpu] || !cpu_ops[cpu]->cpu_suspend) - return -EOPNOTSUPP; return cpu_ops[cpu]->cpu_suspend(index); } |