Commit-ID: d6ff86cfb50a72df820e7e839836d55d245306fb
Gitweb: http://git.kernel.org/tip/d6ff86cfb50a72df820e7e839836d55d245306fb
Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
AuthorDate: Fri, 20 Nov 2009 22:19:46 +0100
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Sat, 21 Nov 2009 14:11:36 +0100
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@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
LKML-Reference: <20091120212508.452227115@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
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 cda17ac..2afb305 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)
--
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