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Subject[tip:perfcounters/urgent] perf_counter: Optimize perf_swcounter_event()
Commit-ID:  f29ac756a40d0f1bb07d682ea521e7b666ff06d5
Gitweb: http://git.kernel.org/tip/f29ac756a40d0f1bb07d682ea521e7b666ff06d5
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Fri, 19 Jun 2009 18:27:26 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 23 Jun 2009 11:42:44 +0200

perf_counter: Optimize perf_swcounter_event()

Similar to tracepoints, use an enable variable to reduce
overhead when unused.

Only look for a counter of a particular event type when we know
there is at least one in the system.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
include/linux/perf_counter.h | 11 ++++++++++-
kernel/perf_counter.c | 18 +++++++++++++++---
2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 89698d8..e7213e4 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -669,7 +669,16 @@ static inline int is_software_counter(struct perf_counter *counter)
(counter->attr.type != PERF_TYPE_HW_CACHE);
}

-extern void perf_swcounter_event(u32, u64, int, struct pt_regs *, u64);
+extern atomic_t perf_swcounter_enabled[PERF_COUNT_SW_MAX];
+
+extern void __perf_swcounter_event(u32, u64, int, struct pt_regs *, u64);
+
+static inline void
+perf_swcounter_event(u32 event, u64 nr, int nmi, struct pt_regs *regs, u64 addr)
+{
+ if (atomic_read(&perf_swcounter_enabled[event]))
+ __perf_swcounter_event(event, nr, nmi, regs, addr);
+}

extern void __perf_counter_mmap(struct vm_area_struct *vma);

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 1a933a2..7515c76 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -3317,8 +3317,8 @@ out:
put_cpu_var(perf_cpu_context);
}

-void
-perf_swcounter_event(u32 event, u64 nr, int nmi, struct pt_regs *regs, u64 addr)
+void __perf_swcounter_event(u32 event, u64 nr, int nmi,
+ struct pt_regs *regs, u64 addr)
{
struct perf_sample_data data = {
.regs = regs,
@@ -3509,9 +3509,19 @@ static const struct pmu *tp_perf_counter_init(struct perf_counter *counter)
}
#endif

+atomic_t perf_swcounter_enabled[PERF_COUNT_SW_MAX];
+
+static void sw_perf_counter_destroy(struct perf_counter *counter)
+{
+ u64 event = counter->attr.config;
+
+ atomic_dec(&perf_swcounter_enabled[event]);
+}
+
static const struct pmu *sw_perf_counter_init(struct perf_counter *counter)
{
const struct pmu *pmu = NULL;
+ u64 event = counter->attr.config;

/*
* Software counters (currently) can't in general distinguish
@@ -3520,7 +3530,7 @@ static const struct pmu *sw_perf_counter_init(struct perf_counter *counter)
* to be kernel events, and page faults are never hypervisor
* events.
*/
- switch (counter->attr.config) {
+ switch (event) {
case PERF_COUNT_SW_CPU_CLOCK:
pmu = &perf_ops_cpu_clock;

@@ -3541,6 +3551,8 @@ static const struct pmu *sw_perf_counter_init(struct perf_counter *counter)
case PERF_COUNT_SW_PAGE_FAULTS_MAJ:
case PERF_COUNT_SW_CONTEXT_SWITCHES:
case PERF_COUNT_SW_CPU_MIGRATIONS:
+ atomic_inc(&perf_swcounter_enabled[event]);
+ counter->destroy = sw_perf_counter_destroy;
pmu = &perf_ops_generic;
break;
}

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