lkml.org 
[lkml]   [2008]   [Nov]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] Inline double_unlock_balance()
Date
Hi,

We have a test case which measures the variation in the amount of time
needed to perform a fixed amount of work on the preempt_rt kernel. We
started seeing deterioration in it's performance recently. The test
should never take more than 10 microseconds, but we started 5-10%
failure rate. Using elimination method, we traced the problem to commit
1b12bbc747560ea68bcc132c3d05699e52271da0 (lockdep: re-annotate
scheduler runqueues). When LOCKDEP is disabled, this patch only adds an
additional function call to double_unlock_balance(). Hence I inlined
double_unlock_balance() and the problem went away. Here is a patch to
make this change.

Thanks,
Sripathi.

lockdep: Inline double_unlock_balance()

Additional function call for double_unlock_balance() causes latency
problems for some test cases on the preempt_rt kernel.

Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>

Index: linux-2.6.27.4/kernel/sched.c
===================================================================
--- linux-2.6.27.4.orig/kernel/sched.c 2008-11-05 05:01:01.000000000 -0800
+++ linux-2.6.27.4/kernel/sched.c 2008-11-05 05:01:20.000000000 -0800
@@ -2812,7 +2812,7 @@
return ret;
}

-static void double_unlock_balance(struct rq *this_rq, struct rq *busiest)
+static inline void double_unlock_balance(struct rq *this_rq, struct rq *busiest)
__releases(busiest->lock)
{
spin_unlock(&busiest->lock);

\
 
 \ /
  Last update: 2008-11-05 14:29    [W:0.053 / U:2.464 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site