From 81520183878a8813c71c9372de28bb70913ba549 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Fri, 20 Nov 2009 22:19:45 +0100
Subject: [PATCH] perf: Optimize perf_swevent_ctx_event()
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: <20091120212508.378188589@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/perf_event.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 8e55b440e28a..cda17acfcaf8 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -3886,15 +3886,10 @@ static void perf_swevent_ctx_event(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_swevent_match(event, type, event_id, data, regs))
perf_swevent_add(event, nr, nmi, data, regs);
}
- rcu_read_unlock();
}
static int *perf_swevent_recursion_context(struct perf_cpu_context *cpuctx)
@@ -3926,9 +3921,9 @@ static void do_perf_sw_event(enum perf_type_id type, u32 event_id,
(*recursion)++;
barrier();
+ rcu_read_lock();
perf_swevent_ctx_event(&cpuctx->ctx, type, event_id,
nr, nmi, data, regs);
- rcu_read_lock();
/*
* doesn't really matter which of the child contexts the
* events ends up in.
--
2.20.1