sched: Turn off child_runs_first

Set child_runs_first default to off.

It hurts 'optimal' make -j<NR_CPUS> workloads as make jobs
get preempted by child tasks, reducing parallelism.

Note, this patch might make existing races in user
applications more prominent than before - so breakages
might be bisected to this commit.

Child-runs-first is broken on SMP to begin with, and we
already had it off briefly in v2.6.23 so most of the
offenders ought to be fixed. Would be nice not to revert
this commit but fix those apps finally ...

Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1252486344.28645.18.camel@marge.simson.net>
[ made the sysctl independent of CONFIG_SCHED_DEBUG, in case
  people want to work around broken apps. ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index e386e5dfcdae..af325a382b1b 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -48,10 +48,10 @@ unsigned int sysctl_sched_min_granularity = 4000000ULL;
 static unsigned int sched_nr_latency = 5;
 
 /*
- * After fork, child runs first. (default) If set to 0 then
+ * After fork, child runs first. If set to 0 (default) then
  * parent will (try to) run first.
  */
-const_debug unsigned int sysctl_sched_child_runs_first = 1;
+unsigned int sysctl_sched_child_runs_first __read_mostly;
 
 /*
  * sys_sched_yield() compat mode