Messages in this thread |  | | Subject | Re: [PATCH 17/33] sched: Update clock of nohz busiest rq before balancing | From | Li Zhong <> | Date | Tue, 08 Jan 2013 18:20:18 +0800 |
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On Tue, 2013-01-08 at 03:08 +0100, Frederic Weisbecker wrote: > move_tasks() and active_load_balance_cpu_stop() both need > to have the busiest rq clock uptodate because they may end > up calling can_migrate_task() that uses rq->clock_task > to determine if the task running in the busiest runqueue > is cache hot. > > Hence if the busiest runqueue is tickless, update its clock > before reading it. > > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> > Cc: Alessio Igor Bogani <abogani@kernel.org> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Chris Metcalf <cmetcalf@tilera.com> > Cc: Christoph Lameter <cl@linux.com> > Cc: Geoff Levand <geoff@infradead.org> > Cc: Gilad Ben Yossef <gilad@benyossef.com> > Cc: Hakan Akkan <hakanakkan@gmail.com> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Li Zhong <zhong@linux.vnet.ibm.com> > Cc: Namhyung Kim <namhyung.kim@lge.com> > Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > Cc: Paul Gortmaker <paul.gortmaker@windriver.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > [ Forward port conflicts ] > Signed-off-by: Steven Rostedt <rostedt@goodmis.org> > --- > kernel/sched/fair.c | 17 +++++++++++++++++ > 1 files changed, 17 insertions(+), 0 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 3d65ac7..e78d81104 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5002,6 +5002,7 @@ static int load_balance(int this_cpu, struct rq *this_rq, > { > int ld_moved, cur_ld_moved, active_balance = 0; > int lb_iterations, max_lb_iterations; > + int clock_updated; > struct sched_group *group; > struct rq *busiest; > unsigned long flags; > @@ -5045,6 +5046,7 @@ redo: > > ld_moved = 0; > lb_iterations = 1; > + clock_updated = 0; > if (busiest->nr_running > 1) { > /* > * Attempt to move tasks. If find_busiest_group has found > @@ -5068,6 +5070,14 @@ more_balance: > */ > cur_ld_moved = move_tasks(&env); > ld_moved += cur_ld_moved; > + > + /* > + * Move tasks may end up calling can_migrate_task() which > + * requires an uptodate value of the rq clock. > + */ > + update_nohz_rq_clock(busiest); > + clock_updated = 1;
According to the change log, it seems these lines should be added before move_tasks() above?
Thanks, Zhong
> + > double_rq_unlock(env.dst_rq, busiest); > local_irq_restore(flags); > > @@ -5163,6 +5173,13 @@ more_balance: > busiest->active_balance = 1; > busiest->push_cpu = this_cpu; > active_balance = 1; > + /* > + * active_load_balance_cpu_stop may end up calling > + * can_migrate_task() which requires an uptodate > + * value of the rq clock. > + */ > + if (!clock_updated) > + update_nohz_rq_clock(busiest); > } > raw_spin_unlock_irqrestore(&busiest->lock, flags); >
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