b5fda7ed5c
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>
42 lines
996 B
C
42 lines
996 B
C
/*
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* ARM64 CPU idle arch support
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*
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* Copyright (C) 2014 ARM Ltd.
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* Author: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/of.h>
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#include <linux/of_device.h>
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#include <asm/cpuidle.h>
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#include <asm/cpu_ops.h>
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int __init arm_cpuidle_init(unsigned int cpu)
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{
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int ret = -EOPNOTSUPP;
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if (cpu_ops[cpu] && cpu_ops[cpu]->cpu_suspend &&
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cpu_ops[cpu]->cpu_init_idle)
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ret = cpu_ops[cpu]->cpu_init_idle(cpu);
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return ret;
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}
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/**
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* cpu_suspend() - function to enter a low-power idle state
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* @arg: argument to pass to CPU suspend operations
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*
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* Return: 0 on success, -EOPNOTSUPP if CPU suspend hook not initialized, CPU
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* operations back-end error code otherwise.
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*/
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int arm_cpuidle_suspend(int index)
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{
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int cpu = smp_processor_id();
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return cpu_ops[cpu]->cpu_suspend(index);
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}
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