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Date: Wed, 07 Oct 2009 16:45:50 +0200
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
To: arun@...ux.vnet.ibm.com
Cc: Joel Schopp <jschopp@...tin.ibm.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
Dipankar Sarma <dipankar@...ibm.com>,
Balbir Singh <balbir@...ibm.com>,
Gautham R Shenoy <ego@...ibm.com>,
Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
linux-arch@...r.kernel.org
Subject: Re: [v7 PATCH 3/7]: x86: refactor x86 idle power management code
and remove all instances of pm_idle.
On Tue, 2009-10-06 at 21:01 +0530, Arun R Bharadwaj wrote:
> +++ linux.trees.git/arch/x86/kernel/process.c
> @@ -9,6 +9,7 @@
> #include <linux/pm.h>
> #include <linux/clockchips.h>
> #include <linux/random.h>
> +#include <linux/cpuidle.h>
> #include <trace/events/power.h>
> #include <asm/system.h>
> #include <asm/apic.h>
> @@ -244,12 +245,6 @@ int sys_vfork(struct pt_regs *regs)
> unsigned long boot_option_idle_override = 0;
> EXPORT_SYMBOL(boot_option_idle_override);
>
> -/*
> - * Powermanagement idle function, if any..
> - */
> -void (*pm_idle)(void);
> -EXPORT_SYMBOL(pm_idle);
> -
> #ifdef CONFIG_X86_32
> /*
> * This halt magic was a workaround for ancient floppy DMA
> @@ -329,17 +324,15 @@ static void do_nothing(void *unused)
> }
>
> /*
> - * cpu_idle_wait - Used to ensure that all the CPUs discard old value of
> - * pm_idle and update to new pm_idle value. Required while changing pm_idle
> - * handler on SMP systems.
> + * cpu_idle_wait - Required while changing idle routine handler on SMP systems.
> *
> - * Caller must have changed pm_idle to the new value before the call. Old
> - * pm_idle value will not be used by any CPU after the return of this function.
> + * Caller must have changed idle routine to the new value before the call. Old
> + * value will not be used by any CPU after the return of this function.
> */
> void cpu_idle_wait(void)
> {
> smp_mb();
> - /* kick all the CPUs so that they exit out of pm_idle */
> + /* kick all the CPUs so that they exit out of idle loop */
> smp_call_function(do_nothing, NULL, 1);
> }
> EXPORT_SYMBOL_GPL(cpu_idle_wait);
> @@ -518,15 +511,59 @@ static void c1e_idle(void)
> default_idle();
> }
>
> +static void (*local_idle)(void);
> +DEFINE_PER_CPU(struct cpuidle_device, idle_devices);
> +
> +struct cpuidle_driver cpuidle_default_driver = {
> + .name = "cpuidle_default",
> +};
> +
> +static int local_idle_loop(struct cpuidle_device *dev, struct cpuidle_state *st)
> +{
> + ktime_t t1, t2;
> + s64 diff;
> + int ret;
> +
> + t1 = ktime_get();
> + local_idle();
> + t2 = ktime_get();
> +
> + diff = ktime_to_us(ktime_sub(t2, t1));
> + if (diff > INT_MAX)
> + diff = INT_MAX;
> + ret = (int) diff;
> +
> + return ret;
> +}
> +
> +static int setup_cpuidle_simple(void)
> +{
> + struct cpuidle_device *dev;
> + int cpu;
> +
> + if (!cpuidle_curr_driver)
> + cpuidle_register_driver(&cpuidle_default_driver);
> +
> + for_each_online_cpu(cpu) {
> + dev = &per_cpu(idle_devices, cpu);
> + dev->cpu = cpu;
> + dev->states[0].enter = local_idle_loop;
> + dev->state_count = 1;
> + cpuidle_register_device(dev);
> + }
> + return 0;
> +}
> +device_initcall(setup_cpuidle_simple);
> +
> void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
> {
> #ifdef CONFIG_SMP
> - if (pm_idle == poll_idle && smp_num_siblings > 1) {
> + if (local_idle == poll_idle && smp_num_siblings > 1) {
> printk(KERN_WARNING "WARNING: polling idle and HT enabled,"
> " performance may degrade.\n");
> }
> #endif
> - if (pm_idle)
> + if (local_idle)
> return;
>
> if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
> @@ -534,18 +571,20 @@ void __cpuinit select_idle_routine(const
> * One CPU supports mwait => All CPUs supports mwait
> */
> printk(KERN_INFO "using mwait in idle threads.\n");
> - pm_idle = mwait_idle;
> + local_idle = mwait_idle;
> } else if (check_c1e_idle(c)) {
> printk(KERN_INFO "using C1E aware idle routine\n");
> - pm_idle = c1e_idle;
> + local_idle = c1e_idle;
> } else
> - pm_idle = default_idle;
> + local_idle = default_idle;
> +
> + return;
> }
>
> void __init init_c1e_mask(void)
> {
> /* If we're using c1e_idle, we need to allocate c1e_mask. */
> - if (pm_idle == c1e_idle)
> + if (local_idle == c1e_idle)
> zalloc_cpumask_var(&c1e_mask, GFP_KERNEL);
> }
>
> @@ -556,7 +595,7 @@ static int __init idle_setup(char *str)
>
> if (!strcmp(str, "poll")) {
> printk("using polling idle threads.\n");
> - pm_idle = poll_idle;
> + local_idle = poll_idle;
> } else if (!strcmp(str, "mwait"))
> force_mwait = 1;
> else if (!strcmp(str, "halt")) {
> @@ -567,7 +606,7 @@ static int __init idle_setup(char *str)
> * To continue to load the CPU idle driver, don't touch
> * the boot_option_idle_override.
> */
> - pm_idle = default_idle;
> + local_idle = default_idle;
> idle_halt = 1;
> return 0;
> } else if (!strcmp(str, "nomwait")) {
What guarantees that the cpuidle bits actually select this
cpuidle_default driver when you do idle=poll?
Also, cpuidle already has a poll loop in it, why duplicate that?
--
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