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Date: Tue, 02 Mar 2010 15:57:22 +0200
From: Aaro Koskinen <aaro.koskinen@...ia.com>
To: ext Martin Schwidefsky <schwidefsky@...ibm.com>
CC: Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Rob van der Heij <rvdheij@...il.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
john stultz <johnstul@...ibm.com>,
Andi Kleen <andi@...stfloor.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>, robert.richter@....com
Subject: Re: [patch 0/2] NOHZ vs. profile/oprofile v2
Hi,
Martin Schwidefsky wrote:
> First version of the hrtimer patch for oprofile. I did not add the
> sysctl yet, if the sysctl is added in oprofile_timer_init it would not
> be available if some better profiling source is available. If it is
> added unconditionally it would only have an effect if the timer
> fallback is used. Both cases are not exactly nice for a user space
> interface.
I wonder what happened to this patch? Some platforms would need
this fix (i.e. the timer mode has to be used due to HW issues).
> ---
> Subject: [PATCH] convert oprofile from timer_hook to hrtimer
>
> From: Martin Schwidefsky <schwidefsky@...ibm.com>
>
> Oprofile is currently broken on systems running with NOHZ enabled.
> A maximum of 1 tick is accounted via the timer_hook if a cpu sleeps
> for a longer period of time. This does bad things to the percentages
> in the profiler output. To solve this problem convert oprofile to
> use a restarting hrtimer instead of the timer_hook.
>
> Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
> ---
>
> drivers/oprofile/oprof.c | 12 ++++--
> drivers/oprofile/oprof.h | 3 +
> drivers/oprofile/timer_int.c | 77 +++++++++++++++++++++++++++++++++++++------
> 3 files changed, 78 insertions(+), 14 deletions(-)
>
> diff -urpN linux-2.6/drivers/oprofile/oprof.c linux-2.6-patched/drivers/oprofile/oprof.c
> --- linux-2.6/drivers/oprofile/oprof.c 2009-06-24 17:21:12.000000000 +0200
> +++ linux-2.6-patched/drivers/oprofile/oprof.c 2009-06-24 17:18:28.000000000 +0200
> @@ -184,22 +184,26 @@ static int __init oprofile_init(void)
> int err;
>
> err = oprofile_arch_init(&oprofile_ops);
> -
> if (err < 0 || timer) {
> printk(KERN_INFO "oprofile: using timer interrupt.\n");
> - oprofile_timer_init(&oprofile_ops);
> + err = oprofile_timer_init(&oprofile_ops);
> + if (err)
> + goto out_arch;
> }
> -
> err = oprofilefs_register();
> if (err)
> - oprofile_arch_exit();
> + goto out_arch;
> + return 0;
>
> +out_arch:
> + oprofile_arch_exit();
> return err;
> }
>
>
> static void __exit oprofile_exit(void)
> {
> + oprofile_timer_exit();
> oprofilefs_unregister();
> oprofile_arch_exit();
> }
> diff -urpN linux-2.6/drivers/oprofile/oprof.h linux-2.6-patched/drivers/oprofile/oprof.h
> --- linux-2.6/drivers/oprofile/oprof.h 2009-06-24 17:21:12.000000000 +0200
> +++ linux-2.6-patched/drivers/oprofile/oprof.h 2009-06-24 17:19:11.000000000 +0200
> @@ -32,7 +32,8 @@ struct super_block;
> struct dentry;
>
> void oprofile_create_files(struct super_block *sb, struct dentry *root);
> -void oprofile_timer_init(struct oprofile_operations *ops);
> +int oprofile_timer_init(struct oprofile_operations *ops);
> +void oprofile_timer_exit(void);
>
> int oprofile_set_backtrace(unsigned long depth);
>
> diff -urpN linux-2.6/drivers/oprofile/timer_int.c linux-2.6-patched/drivers/oprofile/timer_int.c
> --- linux-2.6/drivers/oprofile/timer_int.c 2009-06-24 17:21:12.000000000 +0200
> +++ linux-2.6-patched/drivers/oprofile/timer_int.c 2009-06-24 17:18:44.000000000 +0200
> @@ -13,34 +13,93 @@
> #include <linux/oprofile.h>
> #include <linux/profile.h>
> #include <linux/init.h>
> +#include <linux/cpu.h>
> +#include <linux/hrtimer.h>
> +#include <asm/irq_regs.h>
> #include <asm/ptrace.h>
>
> #include "oprof.h"
>
> -static int timer_notify(struct pt_regs *regs)
> +static DEFINE_PER_CPU(struct hrtimer, oprofile_hrtimer);
> +
> +static enum hrtimer_restart oprofile_hrtimer_notify(struct hrtimer *hrtimer)
> +{
> + oprofile_add_sample(get_irq_regs(), 0);
> + hrtimer_forward_now(hrtimer, ns_to_ktime(TICK_NSEC));
> + return HRTIMER_RESTART;
> +}
> +
> +static void __oprofile_hrtimer_start(void *unused)
> +{
> + struct hrtimer *hrtimer = &__get_cpu_var(oprofile_hrtimer);
> +
> + hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> + hrtimer->function = oprofile_hrtimer_notify;
> +
> + hrtimer_start(hrtimer, ns_to_ktime(TICK_NSEC),
> + HRTIMER_MODE_REL_PINNED);
> +}
> +
> +static int oprofile_hrtimer_start(void)
> {
> - oprofile_add_sample(regs, 0);
> + on_each_cpu(__oprofile_hrtimer_start, NULL, 1);
> return 0;
> }
>
> -static int timer_start(void)
> +static void __oprofile_hrtimer_stop(int cpu)
> {
> - return register_timer_hook(timer_notify);
> + struct hrtimer *hrtimer = &per_cpu(oprofile_hrtimer, cpu);
> +
> + hrtimer_cancel(hrtimer);
> }
>
> +static void oprofile_hrtimer_stop(void)
> +{
> + int cpu;
> + for_each_online_cpu(cpu)
> + __oprofile_hrtimer_stop(cpu);
> +}
>
> -static void timer_stop(void)
> +static int __cpuinit oprofile_cpu_notify(struct notifier_block *self,
> + unsigned long action, void *hcpu)
> {
> - unregister_timer_hook(timer_notify);
> + long cpu = (long) hcpu;
> +
> + switch (action) {
> + case CPU_ONLINE:
> + case CPU_ONLINE_FROZEN:
> + smp_call_function_single(cpu, __oprofile_hrtimer_start,
> + NULL, 1);
> + break;
> + case CPU_DEAD:
> + case CPU_DEAD_FROZEN:
> + __oprofile_hrtimer_stop(cpu);
> + break;
> + }
> + return NOTIFY_OK;
> }
>
> +static struct notifier_block __refdata oprofile_cpu_notifier = {
> + .notifier_call = oprofile_cpu_notify,
> +};
>
> -void __init oprofile_timer_init(struct oprofile_operations *ops)
> +int __init oprofile_timer_init(struct oprofile_operations *ops)
> {
> + int rc;
> +
> + rc = register_hotcpu_notifier(&oprofile_cpu_notifier);
> + if (rc)
> + return rc;
> ops->create_files = NULL;
> ops->setup = NULL;
> ops->shutdown = NULL;
> - ops->start = timer_start;
> - ops->stop = timer_stop;
> + ops->start = oprofile_hrtimer_start;
> + ops->stop = oprofile_hrtimer_stop;
> ops->cpu_type = "timer";
> + return 0;
> +}
> +
> +void __exit oprofile_timer_exit(void)
> +{
> + unregister_hotcpu_notifier(&oprofile_cpu_notifier);
> }
>
> ---
>
--
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