From: Con Kolivas <kernel@xxxxxxxxxxx>
When kswapd is awoken due to reclaim by a running task, set the priority
of kswapd to that of the task allocating pages thus making memory reclaim
cpu activity affected by nice level.
[rientjes@xxxxxxxxxx: refactor for current]
Cc: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: Con Kolivas <kernel@xxxxxxxxxxx>
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
mm/vmscan.c | 33 ++++++++++++++++++++++++++++++++-
1 files changed, 32 insertions(+), 1 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1658,6 +1658,33 @@ static void shrink_zone(int priority, struct zone *zone,
}
/*
+ * Helper functions to adjust nice level of kswapd, based on the priority of
+ * the task allocating pages. If it is already higher priority we do not
+ * demote its nice level since it is still working on behalf of a higher
+ * priority task. With kernel threads we leave it at nice 0.
+ *
+ * We don't ever run kswapd real time, so if a real time task calls kswapd we
+ * set it to highest SCHED_NORMAL priority.
+ */
+static int effective_sc_prio(struct task_struct *p)
+{
+ if (likely(p->mm)) {
+ if (rt_task(p))
+ return -20;
+ return task_nice(p);
+ }
+ return 0;
+}
+
+static void set_kswapd_nice(struct task_struct *kswapd, int active)
+{
+ long nice = effective_sc_prio(current);
+
+ if (task_nice(kswapd) > nice || !active)
+ set_user_nice(kswapd, nice);
+}
+
+/*
* This is the direct reclaim path, for page-allocating processes. We only
* try to reclaim pages from zones which will satisfy the caller's allocation
* request.
@@ -2257,6 +2284,7 @@ static int kswapd(void *p)
}
}
+ set_user_nice(tsk, 0);
order = pgdat->kswapd_max_order;
}
finish_wait(&pgdat->kswapd_wait, &wait);
@@ -2281,6 +2309,7 @@ static int kswapd(void *p)
void wakeup_kswapd(struct zone *zone, int order)
{
pg_data_t *pgdat;
+ int active;
if (!populated_zone(zone))
return;
@@ -2292,7 +2321,9 @@ void wakeup_kswapd(struct zone *zone, int order)
pgdat->kswapd_max_order = order;
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
return;
- if (!waitqueue_active(&pgdat->kswapd_wait))
+ active = waitqueue_active(&pgdat->kswapd_wait);
+ set_kswapd_nice(pgdat->kswapd, active);
+ if (!active)
return;
wake_up_interruptible(&pgdat->kswapd_wait);
}
--
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