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Subject[tip:perfcounters/core] perf_counter: theres more to overflow than writing events
Commit-ID:  f6c7d5fe58b4846ee0cb4b98b6042489705eced4
Gitweb: http://git.kernel.org/tip/f6c7d5fe58b4846ee0cb4b98b6042489705eced4
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Mon, 6 Apr 2009 11:45:04 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 7 Apr 2009 10:48:56 +0200

perf_counter: theres more to overflow than writing events

Prepare for more generic overflow handling. The new perf_counter_overflow()
method will handle the generic bits of the counter overflow, and can return
a !0 return value, in which case the counter should be (soft) disabled, so
that it won't count until it's properly disabled.

XXX: do powerpc and swcounter

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090406094517.812109629@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
arch/powerpc/kernel/perf_counter.c | 2 +-
arch/x86/kernel/cpu/perf_counter.c | 3 ++-
include/linux/perf_counter.h | 4 ++--
kernel/perf_counter.c | 29 +++++++++++++++++++++++------
4 files changed, 28 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/kernel/perf_counter.c b/arch/powerpc/kernel/perf_counter.c
index 0a4d14f..f88c35d 100644
--- a/arch/powerpc/kernel/perf_counter.c
+++ b/arch/powerpc/kernel/perf_counter.c
@@ -732,7 +732,7 @@ static void record_and_restart(struct perf_counter *counter, long val,
* Finally record data if requested.
*/
if (record)
- perf_counter_output(counter, 1, regs);
+ perf_counter_overflow(counter, 1, regs);
}

/*
diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index 4384158..1116a41 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -800,7 +800,8 @@ again:
continue;

perf_save_and_restart(counter);
- perf_counter_output(counter, nmi, regs);
+ if (perf_counter_overflow(counter, nmi, regs))
+ __pmc_generic_disable(counter, &counter->hw, bit);
}

hw_perf_ack_status(ack);
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 977fb15..ca2d4df 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -491,8 +491,8 @@ extern int hw_perf_group_sched_in(struct perf_counter *group_leader,
struct perf_counter_context *ctx, int cpu);
extern void perf_counter_update_userpage(struct perf_counter *counter);

-extern void perf_counter_output(struct perf_counter *counter,
- int nmi, struct pt_regs *regs);
+extern int perf_counter_overflow(struct perf_counter *counter,
+ int nmi, struct pt_regs *regs);
/*
* Return 1 for a software counter, 0 for a hardware counter
*/
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 0a2ade2..195e976 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1800,8 +1800,8 @@ static void perf_output_end(struct perf_output_handle *handle)
rcu_read_unlock();
}

-void perf_counter_output(struct perf_counter *counter,
- int nmi, struct pt_regs *regs)
+static void perf_counter_output(struct perf_counter *counter,
+ int nmi, struct pt_regs *regs)
{
int ret;
u64 record_type = counter->hw_event.record_type;
@@ -2034,6 +2034,17 @@ void perf_counter_munmap(unsigned long addr, unsigned long len,
}

/*
+ * Generic counter overflow handling.
+ */
+
+int perf_counter_overflow(struct perf_counter *counter,
+ int nmi, struct pt_regs *regs)
+{
+ perf_counter_output(counter, nmi, regs);
+ return 0;
+}
+
+/*
* Generic software counter infrastructure
*/

@@ -2077,6 +2088,7 @@ static void perf_swcounter_set_period(struct perf_counter *counter)

static enum hrtimer_restart perf_swcounter_hrtimer(struct hrtimer *hrtimer)
{
+ enum hrtimer_restart ret = HRTIMER_RESTART;
struct perf_counter *counter;
struct pt_regs *regs;

@@ -2092,12 +2104,14 @@ static enum hrtimer_restart perf_swcounter_hrtimer(struct hrtimer *hrtimer)
!counter->hw_event.exclude_user)
regs = task_pt_regs(current);

- if (regs)
- perf_counter_output(counter, 0, regs);
+ if (regs) {
+ if (perf_counter_overflow(counter, 0, regs))
+ ret = HRTIMER_NORESTART;
+ }

hrtimer_forward_now(hrtimer, ns_to_ktime(counter->hw.irq_period));

- return HRTIMER_RESTART;
+ return ret;
}

static void perf_swcounter_overflow(struct perf_counter *counter,
@@ -2105,7 +2119,10 @@ static void perf_swcounter_overflow(struct perf_counter *counter,
{
perf_swcounter_update(counter);
perf_swcounter_set_period(counter);
- perf_counter_output(counter, nmi, regs);
+ if (perf_counter_overflow(counter, nmi, regs))
+ /* soft-disable the counter */
+ ;
+
}

static int perf_swcounter_match(struct perf_counter *counter,

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