Kirill Tkhai <[email protected]> writes: > We update decay_counter in update_cfs_rq_blocked_load() > only. This function is always called with rq lock locked, > so we can kill atomic actions. > > Signed-off-by: Kirill Tkhai <[email protected]> > --- > kernel/sched/fair.c | 11 ++++++----- > kernel/sched/sched.h | 2 +- > 2 files changed, 7 insertions(+), 6 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 5f3b5a7..af990c4 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -2570,7 +2570,7 @@ static __always_inline int > __update_entity_runnable_avg(u64 now, > static inline u64 __synchronize_entity_decay(struct sched_entity *se) > { > struct cfs_rq *cfs_rq = cfs_rq_of(se); > - u64 decays = atomic64_read(&cfs_rq->decay_counter); > + u64 decays = ACCESS_ONCE(cfs_rq->decay_counter);
This is called without rq lock held from migrate_task_rq_fair. (We could technically change the atomic_add to atomic64_set(atomic64_read() + x), but I don't know that that is a win) Now, we could do a min_vruntime-style two-copy thing if this atomic usage is a hot spot on 32-bit, we just didn't bother initially. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
