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perf_counter: Optimize perf_swcounter_event()

Browse source 
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>
This commit is contained in:
Peter Zijlstra 2009-06-19 18:27:26 +02:00 committed by Ingo Molnar
parent 3d906ef10a
commit f29ac756a4
2 changed files with 25 additions and 4 deletions
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11
include/linux/perf_counter.h
View file

@ -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);

18
kernel/perf_counter.c
View file

@ -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;
}