The checks for the scan time in task_mm_cid_work are now superfluous
since the task runs in a delayed_work and the minimum periodicity is
already implied.
This patch removes those checks and the field from the mm_struct.
Additionally, we include a simple check to quickly terminate the
function if we have no work to be done (i.e. no mm_cid is allocated).
This is helpful for tasks that sleep for a long time, but also for
terminated task. We are no longer following the process' state, hence
the function continues to run after a process terminates but before its
mm is freed.
Signed-off-by: Gabriele Monaco <gmonaco@xxxxxxxxxx>
---
include/linux/mm_types.h | 7 -------
kernel/sched/core.c | 19 +++----------------
2 files changed, 3 insertions(+), 23 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 92acb827fee4..8a76a1c09234 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -829,12 +829,6 @@ struct mm_struct {
* runqueue locks.
*/
struct mm_cid __percpu *pcpu_cid;
- /*
- * @mm_cid_next_scan: Next mm_cid scan (in jiffies).
- *
- * When the next mm_cid scan is due (in jiffies).
- */
- unsigned long mm_cid_next_scan;
/**
* @nr_cpus_allowed: Number of CPUs allowed for mm.
*
@@ -1228,7 +1222,6 @@ static inline int mm_alloc_cid_noprof(struct mm_struct *mm, struct task_struct *
return -ENOMEM;
mm_init_cid(mm, p);
INIT_DELAYED_WORK(&mm->mm_cid_work, task_mm_cid_work);
- mm->mm_cid_next_scan = jiffies + msecs_to_jiffies(MM_CID_SCAN_DELAY);
schedule_delayed_work(&mm->mm_cid_work,
msecs_to_jiffies(MM_CID_SCAN_DELAY));
return 0;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e3b27b73301c..30d78fe14eff 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10520,28 +10520,15 @@ static void sched_mm_cid_remote_clear_weight(struct mm_struct *mm, int cpu,
void task_mm_cid_work(struct work_struct *work)
{
- unsigned long now = jiffies, old_scan, next_scan;
struct cpumask *cidmask;
struct delayed_work *delayed_work = container_of(work, struct delayed_work, work);
struct mm_struct *mm = container_of(delayed_work, struct mm_struct, mm_cid_work);
int weight, cpu;
- old_scan = READ_ONCE(mm->mm_cid_next_scan);
- next_scan = now + msecs_to_jiffies(MM_CID_SCAN_DELAY);
- if (!old_scan) {
- unsigned long res;
-
- res = cmpxchg(&mm->mm_cid_next_scan, old_scan, next_scan);
- if (res != old_scan)
- old_scan = res;
- else
- old_scan = next_scan;
- }
- if (time_before(now, old_scan))
- goto out;
- if (!try_cmpxchg(&mm->mm_cid_next_scan, &old_scan, next_scan))
- goto out;
cidmask = mm_cidmask(mm);
+ /* Nothing to clear for now */
+ if (cpumask_empty(cidmask))
+ goto out;
/* Clear cids that were not recently used. */
for_each_possible_cpu(cpu)
sched_mm_cid_remote_clear_old(mm, cpu);
--
2.47.1
