rpms/kernel/F-11 sched-update-the-clock-of-runqueue-select-task-rq-selected.patch, NONE, 1.1 kernel.spec, 1.1766, 1.1767

[Chuck Ebbert]

Author: cebbert

Update of /cvs/pkgs/rpms/kernel/F-11
In directory cvs1.fedora.phx.redhat.com:/tmp/cvs-serv16465

Modified Files:
	kernel.spec 
Added Files:
	sched-update-the-clock-of-runqueue-select-task-rq-selected.patch 
Log Message:
Scheduler wakeup patch, fixes high latency on wakeup
  (sched-update-the-clock-of-runqueue-select-task-rq-selected.patch)

sched-update-the-clock-of-runqueue-select-task-rq-selected.patch:
 sched.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- NEW FILE sched-update-the-clock-of-runqueue-select-task-rq-selected.patch ---
From: Mike Galbraith <efault at gmx.de>
Date: Fri, 9 Oct 2009 06:35:03 +0000 (+0200)
Subject: sched: Update the clock of runqueue select_task_rq() selected
X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=f5dc375

sched: Update the clock of runqueue select_task_rq() selected

[ backport to 2.6.3[01] : <cebbert at redhat.com> ]

In try_to_wake_up(), we update the runqueue clock, but
select_task_rq() may select a different runqueue than the one we
updated, leaving the new runqueue's clock stale for a bit.

This patch cures occasional huge latencies reported by latencytop
when coming out of idle on a mostly idle NO_HZ box.

Signed-off-by: Mike Galbraith <efault at gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra at chello.nl>
LKML-Reference: <1255070103.7639.30.camel at marge.simson.net>
Signed-off-by: Ingo Molnar <mingo at elte.hu>
---

diff a/kernel/sched.c b/kernel/sched.c
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2344,7 +2344,7 @@ static int try_to_wake_up(struct task_st
 	int cpu, orig_cpu, this_cpu, success = 0;
 	unsigned long flags;
 	long old_state;
-	struct rq *rq;
+	struct rq *rq, *orig_rq;
 
 	if (!sched_feat(SYNC_WAKEUPS))
 		sync = 0;
@@ -2366,7 +2366,7 @@ static int try_to_wake_up(struct task_st
 #endif
 
 	smp_wmb();
-	rq = task_rq_lock(p, &flags);
+	rq = orig_rq = task_rq_lock(p, &flags);
 	update_rq_clock(rq);
 	old_state = p->state;
 	if (!(old_state & state))
@@ -2389,6 +2389,8 @@ static int try_to_wake_up(struct task_st
 		task_rq_unlock(rq, &flags);
 		/* might preempt at this point */
 		rq = task_rq_lock(p, &flags);
+		if (rq != orig_rq)
+			update_rq_clock(rq);
 		old_state = p->state;
 		if (!(old_state & state))
 			goto out;


Index: kernel.spec
===================================================================
RCS file: /cvs/pkgs/rpms/kernel/F-11/kernel.spec,v
retrieving revision 1.1766
retrieving revision 1.1767
diff -u -p -r1.1766 -r1.1767
--- kernel.spec	16 Oct 2009 11:00:06 -0000	1.1766
+++ kernel.spec	17 Oct 2009 12:59:18 -0000	1.1767
@@ -806,6 +806,8 @@ Patch15900: ax25-fix-possible-oops-in-ax
 # netlink security fix (CVE-2009-3612)
 Patch16000: netlink-fix-typo-in-initialization.patch
 
+Patch16200: sched-update-the-clock-of-runqueue-select-task-rq-selected.patch
+
 %endif
 
 BuildRoot: %{_tmppath}/kernel-%{KVERREL}-root
@@ -1509,6 +1511,8 @@ ApplyPatch ax25-fix-possible-oops-in-ax2
 # netlink security fix (CVE-2009-3612)
 ApplyPatch netlink-fix-typo-in-initialization.patch
 
+ApplyPatch sched-update-the-clock-of-runqueue-select-task-rq-selected.patch
+
 # END OF PATCH APPLICATIONS
 
 %endif
@@ -2097,6 +2101,10 @@ fi
 # and build.
 
 %changelog
+* Sat Oct 17 2009 Chuck Ebbert <cebbert at redhat.com> 2.6.30.9-88
+- Scheduler wakeup patch, fixes high latency on wakeup
+  (sched-update-the-clock-of-runqueue-select-task-rq-selected.patch)
+
 * Fri Oct 16 2009 Chuck Ebbert <cebbert at redhat.com> 2.6.30.9-87
 - Fix uninitialized data leak in netlink (CVE-2009-3612)