rq->clock_task may be updated between the two calls of rq_clock_task() in update_curr_dl(). Calling rq_clock_task() only once makes it more accurate and efficient, taking update_curr() as reference.
Signed-off-by: Wen Yang <[email protected]> Reviewed-by: Jiang Biao <[email protected]> Suggested-by: Peter Zijlstra <[email protected]> --- kernel/sched/deadline.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 2473736..a32209c 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1115,6 +1115,7 @@ static void update_curr_dl(struct rq *rq) struct task_struct *curr = rq->curr; struct sched_dl_entity *dl_se = &curr->dl; u64 delta_exec; + u64 now; if (!dl_task(curr) || !on_dl_rq(dl_se)) return; @@ -1127,7 +1128,8 @@ static void update_curr_dl(struct rq *rq) * natural solution, but the full ramifications of this * approach need further study. */ - delta_exec = rq_clock_task(rq) - curr->se.exec_start; + now = rq_clock_task(rq); + delta_exec = now - curr->se.exec_start; if (unlikely((s64)delta_exec <= 0)) { if (unlikely(dl_se->dl_yielded)) goto throttle; @@ -1143,7 +1145,7 @@ static void update_curr_dl(struct rq *rq) curr->se.sum_exec_runtime += delta_exec; account_group_exec_runtime(curr, delta_exec); - curr->se.exec_start = rq_clock_task(rq); + curr->se.exec_start = now; cgroup_account_cputime(curr, delta_exec); sched_rt_avg_update(rq, delta_exec); -- 1.8.3.1
