On 2/25/24 21:11, Jens Axboe wrote:
On 2/25/24 9:43 AM, Jens Axboe wrote:
If you are motivated, please dig into it. If not, I guess I will take a
look this week.
I tried to split the atomic as mentioned, but I don't think anybody
cares, it was 0.1% in perf, so wouldn't even be benchmarkeable,
and it's iowait only patch anyway. If anything you'd need to read
two vars every tick now, so nevermind
The straight forward approach - add a nr_short_wait and ->in_short_wait
and ensure that the idle governor factors that in. Not sure how
palatable it is, would be nice fold iowait under this, but doesn't
really work with how we pass back the previous state.
It might look nicer if instead adding nr_short_waiters you'd
do nr_iowait_account for the iowait% and leave nr_iowait
for cpufreq.
The block iowaiting / io_schedule / etc. would need to set
both flags...
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9116bcc90346..dc7a08db8921 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3790,6 +3790,8 @@ ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
if (p->in_iowait) {
delayacct_blkio_end(p);
atomic_dec(&task_rq(p)->nr_iowait);
+ } else if (p->in_short_wait) {
+ atomic_dec(&task_rq(p)->nr_short_wait);
}
activate_task(rq, p, en_flags);
@@ -4356,6 +4358,8 @@ int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
if (p->in_iowait) {
delayacct_blkio_end(p);
atomic_dec(&task_rq(p)->nr_iowait);
+ } else if (p->in_short_wait) {
+ atomic_dec(&task_rq(p)->nr_short_wait);
... which would get this branch folded into the previous one,
which should be more welcome by the sched guys.
--
Pavel Begunkov
