Re: [PATCH] sched: fix env->src_cpu for active migration

Hi Damien,

Thanks for the test and the feedback. Could you send me the sched_domain configuration of your machine with the kernel that boots on your machine ? It's available in /proc/sys/kernel/sched_domain/cpu*/

This should not have any impact on your machine but it looks like it have one.

Regards, Vincent

On 13 February 2013 07:18, Damien Wyart damien.wyart@gmail.com wrote:

Hi,

I tested this on top of 3.8-rc7 and this made the machine (x86_64, Core i7 920) unable to boot (very early as nothing at all is displayed on screen). Nothing in the kernel log (after booting with a working kernel).

Double-checked by just backing out only this patch and this made the machine boot again.

Damien

...

need_active_balance uses env->src_cpu which is set only if there is more than 1 task on the run queue. We must set the src_cpu field unconditionnally otherwise the test "env->src_cpu > env->dst_cpu" will always fail if there is only 1 task on the run queue

Signed-off-by: Vincent Guittot vincent.guittot@linaro.org

kernel/sched/fair.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 81fa536..32938ea 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5044,6 +5044,10 @@ redo:

  ld_moved = 0;
  lb_iterations = 1;

• env.src_cpu   = busiest->cpu;
  

• env.src_rq    = busiest;
  

• if (busiest->nr_running > 1) {
          /*
           * Attempt to move tasks. If find_busiest_group has found
  

@@ -5052,8 +5056,6 @@ redo: * correctly treated as an imbalance. */ env.flags |= LBF_ALL_PINNED;

•         env.src_cpu   = busiest->cpu;
  

•         env.src_rq    = busiest;
          env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
  
          update_h_load(env.src_cpu);