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>
parent
7d7b4ae4
Please register or sign in to comment