On Mon, Apr 29, 2013 at 11:17:17PM -0400, kosaki.motoh...@gmail.com wrote: > From: KOSAKI Motohiro <kosaki.motoh...@jp.fujitsu.com> > > rq lock in task_sched_runtime() is necessary for two reasons. 1) > accessing se.sum_exec_runtime is inatomic on 32bit and 2) > do_task_delta_exec() require it. > > And then, 64bit can avoid holds rq lock when add_delta is false. > > Signed-off-by: KOSAKI Motohiro <kosaki.motoh...@jp.fujitsu.com> > --- > kernel/sched/core.c | 6 ++++++ > 1 files changed, 6 insertions(+), 0 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index b817e6d..24ba1c6 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -2657,6 +2657,12 @@ unsigned long long task_sched_runtime(struct > task_struct *p, bool add_delta) > struct rq *rq; > u64 ns = 0; > > + /* Micro optimization. */
Instead of the above; how about something like: /* 64-bit doesn't need locks to atomically read a 64bit value */ > +#ifdef CONFIG_64BIT > + if (!add_delta) > + return p->se.sum_exec_runtime; > +#endif > + > rq = task_rq_lock(p, &flags); > ns = p->se.sum_exec_runtime; > if (add_delta) > -- > 1.7.1 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
