[RFC PATCH] psi : calc psi memstall time more precisely

From: Huangzhaoyang
Date: Thu Sep 09 2021 - 10:02:57 EST


From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>

psi's memstall time is counted as simple as exit - entry so far, which ignore
the task's off cpu time. Fix it by calc the percentage of off time via task and
rq's util and runq load.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
kernel/sched/psi.c | 22 +++++++++++++++++++++-
1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index cc25a3c..6812c7e 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -182,6 +182,8 @@ struct psi_group psi_system = {

static void psi_avgs_work(struct work_struct *work);

+static unsigned long psi_memtime_fixup(u32 growth);
+
static void group_init(struct psi_group *group)
{
int cpu;
@@ -492,6 +494,23 @@ static u64 window_update(struct psi_window *win, u64 now, u64 value)
return growth;
}

+static unsigned long psi_memtime_fixup(u32 growth)
+{
+ struct rq *rq = task_rq(current);
+ unsigned long growth_fixed = (unsigned long)growth;
+
+ if !(current->policy == SCHED_NORMAL || current->policy == SCHED_BATCH)
+ return growth_fixed;
+
+ if ((current->in_memstall)
+ && (current->se.avg.util_avg <= rq->cfs.avg.util_avg)
+ && current->se.avg.util_avg != 0)
+ growth_fixed = div64_ul((current->se.avg.util_avg + 1) * growth,
+ rq->cfs.avg.util_avg + rq->avg_rt.util_avg + 1);
+
+ return growth_fixed;
+}
+
static void init_triggers(struct psi_group *group, u64 now)
{
struct psi_trigger *t;
@@ -658,6 +677,7 @@ static void record_times(struct psi_group_cpu *groupc, u64 now)
}

if (groupc->state_mask & (1 << PSI_MEM_SOME)) {
+ delta = psi_memtime_fixup(delta);
groupc->times[PSI_MEM_SOME] += delta;
if (groupc->state_mask & (1 << PSI_MEM_FULL))
groupc->times[PSI_MEM_FULL] += delta;
@@ -928,8 +948,8 @@ void psi_memstall_leave(unsigned long *flags)
*/
rq = this_rq_lock_irq(&rf);

- current->in_memstall = 0;
psi_task_change(current, TSK_MEMSTALL, 0);
+ current->in_memstall = 0;

rq_unlock_irq(rq, &rf);
}
--
1.9.1