From 128fb95650b3273a8dc9ba5514b6fe7db8ea30bf Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Wed, 6 Dec 2006 20:36:50 -0800
Subject: [PATCH] [PATCH] taskstats_exit_alloc: optimize/simplify
If there are no listeners, every task does unneeded kmem_cache alloc/free on
exit. We don't need listeners->sem for 'if (!list_empty())' check. Yes, we may
have a false positive, but this doesn't differ from the case when the listener
is unregistered after we drop the semaphore. So we don't need to do allocation
beforehand.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Balbir Singh <balbir@in.ibm.com>
Acked-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
kernel/taskstats.c | 17 ++++-------------
1 file changed, 4 insertions(+), 13 deletions(-)
diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index f5f92014ae982..d9d7c35762388 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -416,7 +416,6 @@ static int taskstats_user_cmd(struct sk_buff *skb, struct genl_info *info)
void taskstats_exit_alloc(struct taskstats **ptidstats, unsigned int *mycpu)
{
struct listener_list *listeners;
- struct taskstats *tmp;
/*
* This is the cpu on which the task is exiting currently and will
* be the one for which the exit event is sent, even if the cpu
@@ -424,19 +423,11 @@ void taskstats_exit_alloc(struct taskstats **ptidstats, unsigned int *mycpu)
*/
*mycpu = raw_smp_processor_id();
- *ptidstats = NULL;
- tmp = kmem_cache_zalloc(taskstats_cache, GFP_KERNEL);
- if (!tmp)
- return;
-
listeners = &per_cpu(listener_array, *mycpu);
- down_read(&listeners->sem);
- if (!list_empty(&listeners->list)) {
- *ptidstats = tmp;
- tmp = NULL;
- }
- up_read(&listeners->sem);
- kfree(tmp);
+
+ *ptidstats = NULL;
+ if (!list_empty(&listeners->list))
+ *ptidstats = kmem_cache_zalloc(taskstats_cache, GFP_KERNEL);
}
/* Send pid data out on exit */
--
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