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| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2009-11-20 22:19:46 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-11-21 14:11:36 +0100 |
| commit | d6ff86cfb50a72df820e7e839836d55d245306fb (patch) | |
| tree | e615cbbc693da8c5000d5eb3a022207c7f85605a /kernel/perf_event.c | |
| parent | 81520183878a8813c71c9372de28bb70913ba549 (diff) | |
| download | lwn-d6ff86cfb50a72df820e7e839836d55d245306fb.tar.gz lwn-d6ff86cfb50a72df820e7e839836d55d245306fb.zip | |
perf: Optimize perf_event_task_ctx()
Remove a rcu_read_{,un}lock() pair and a few conditionals.
We can remove the rcu_read_lock() by increasing the scope of one
in the calling function.
We can do away with the system_state check if the machine still
boots after this patch (seems to be the case).
We can do away with the list_empty() check because the bare
list_for_each_entry_rcu() reduces to that now that we've removed
everything else.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20091120212508.452227115@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/perf_event.c')
| -rw-r--r-- | kernel/perf_event.c | 7 |
1 files changed, 1 insertions, 6 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c index cda17acfcaf8..2afb305944af 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -3267,15 +3267,10 @@ static void perf_event_task_ctx(struct perf_event_context *ctx, { struct perf_event *event; - if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list)) - return; - - rcu_read_lock(); list_for_each_entry_rcu(event, &ctx->event_list, event_entry) { if (perf_event_task_match(event)) perf_event_task_output(event, task_event); } - rcu_read_unlock(); } static void perf_event_task_event(struct perf_task_event *task_event) @@ -3283,11 +3278,11 @@ static void perf_event_task_event(struct perf_task_event *task_event) struct perf_cpu_context *cpuctx; struct perf_event_context *ctx = task_event->task_ctx; + rcu_read_lock(); cpuctx = &get_cpu_var(perf_cpu_context); perf_event_task_ctx(&cpuctx->ctx, task_event); put_cpu_var(perf_cpu_context); - rcu_read_lock(); if (!ctx) ctx = rcu_dereference(task_event->task->perf_event_ctxp); if (ctx) |