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Message-ID: <20100302160110.5fd14f5f@mschwide.boeblingen.de.ibm.com>
Date: Tue, 2 Mar 2010 16:01:10 +0100
From: Martin Schwidefsky <schwidefsky@...ibm.com>
To: Aaro Koskinen <aaro.koskinen@...ia.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
On Tue, 02 Mar 2010 15:57:22 +0200
Aaro Koskinen <aaro.koskinen@...ia.com> wrote:
> 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).
After SH removed their oprofile hook there is nothing left that would
prevent us from converting oprofile to hrtimer. Just a matter of
reminding me and have me try again ;-)
Patch against current git. Ingo, Thomas: one for the timer tree I guess.
--
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 | 78 ++++++++++++++++++++++++++++++++++++++-----
3 files changed, 79 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 2010-02-24 19:52:17.000000000 +0100
+++ linux-2.6-patched/drivers/oprofile/oprof.c 2010-03-02 15:57:02.000000000 +0100
@@ -253,22 +253,26 @@ 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 2010-02-24 19:52:17.000000000 +0100
+++ linux-2.6-patched/drivers/oprofile/oprof.h 2010-03-02 15:57:02.000000000 +0100
@@ -34,7 +34,8 @@ 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);
int oprofile_set_timeout(unsigned long time);
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 2010-02-24 19:52:17.000000000 +0100
+++ linux-2.6-patched/drivers/oprofile/timer_int.c 2010-03-02 15:57:02.000000000 +0100
@@ -13,34 +13,94 @@
#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);
}
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
--
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