Messages in this thread Patch in this message | | | Date | Fri, 8 May 2009 18:39:32 GMT | From | tip-bot for Peter Zijlstra <> | Subject | [tip:perfcounters/core] perf_counter: optimize perf_counter_task_tick() |
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Commit-ID: 7fc23a5380797012e92a9633169440f2f4a21253 Gitweb: http://git.kernel.org/tip/7fc23a5380797012e92a9633169440f2f4a21253 Author: Peter Zijlstra <a.p.zijlstra@chello.nl> AuthorDate: Fri, 8 May 2009 18:52:21 +0200 Committer: Ingo Molnar <mingo@elte.hu> CommitDate: Fri, 8 May 2009 20:36:57 +0200
perf_counter: optimize perf_counter_task_tick()
perf_counter_task_tick() does way too much work to find out there's nothing to do. Provide an easy short-circuit for the normal case where there are no counters on the system.
[ Impact: micro-optimization ]
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: <20090508170028.750619201@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
--- kernel/perf_counter.c | 13 +++++++++++-- 1 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index 60e55f0..fdb0d24 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -39,6 +39,7 @@ int perf_max_counters __read_mostly = 1; static int perf_reserved_percpu __read_mostly; static int perf_overcommit __read_mostly = 1; +static atomic_t nr_counters __read_mostly; static atomic_t nr_mmap_tracking __read_mostly; static atomic_t nr_munmap_tracking __read_mostly; static atomic_t nr_comm_tracking __read_mostly; @@ -1076,8 +1077,14 @@ static void rotate_ctx(struct perf_counter_context *ctx) void perf_counter_task_tick(struct task_struct *curr, int cpu) { - struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu); - struct perf_counter_context *ctx = &curr->perf_counter_ctx; + struct perf_cpu_context *cpuctx; + struct perf_counter_context *ctx; + + if (!atomic_read(&nr_counters)) + return; + + cpuctx = &per_cpu(perf_cpu_context, cpu); + ctx = &curr->perf_counter_ctx; perf_counter_cpu_sched_out(cpuctx); perf_counter_task_sched_out(curr, cpu); @@ -1197,6 +1204,7 @@ static void free_counter(struct perf_counter *counter) { perf_pending_sync(counter); + atomic_dec(&nr_counters); if (counter->hw_event.mmap) atomic_dec(&nr_mmap_tracking); if (counter->hw_event.munmap) @@ -2861,6 +2869,7 @@ done: counter->pmu = pmu; + atomic_inc(&nr_counters); if (counter->hw_event.mmap) atomic_inc(&nr_mmap_tracking); if (counter->hw_event.munmap)
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