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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2009-11-20 22:19:48 +0100
committerIngo Molnar <mingo@elte.hu>2009-11-21 14:11:37 +0100
commitf6d9dd237da400effb265f3554c64413f8a3e7b4 (patch)
treed06e7ec3385697a638b18c6890c087f0ac8e329b /kernel
parentf6595f3a9680c86b6332f881a7ae2cbbcfdc8619 (diff)
perf: Optimize perf_event_mmap_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: <20091120212508.606459548@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/perf_event.c7
1 files changed, 1 insertions, 6 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 4deefaace90..68fbf4ff688 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -3493,15 +3493,10 @@ static void perf_event_mmap_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_mmap_match(event, mmap_event))
perf_event_mmap_output(event, mmap_event);
}
- rcu_read_unlock();
}
static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
@@ -3557,11 +3552,11 @@ got_name:
mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;
+ rcu_read_lock();
cpuctx = &get_cpu_var(perf_cpu_context);
perf_event_mmap_ctx(&cpuctx->ctx, mmap_event);
put_cpu_var(perf_cpu_context);
- rcu_read_lock();
/*
* doesn't really matter which of the child contexts the
* events ends up in.