[PATCH v2] vmpressure: consider "scanned < reclaimed" case when calculating a pressure level.

[Hyunhee Kim <hyunhee.kim@samsung.com>]

In vmpressure, the pressure level is calculated based on the ratio
of how many pages were scanned vs. reclaimed in a given time window.
However, there is a possibility that "scanned < reclaimed" in such a
case, when reclaiming ends by fatal signal in shrink_inactive_list.
So, with this patch, we just return "low" level when "scanned < reclaimed"
happens not to have userland miss reclaim activity.

Signed-off-by: Hyunhee Kim <hyunhee.kim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
 mm/vmpressure.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index 736a601..8c60cad 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -119,6 +119,14 @@ static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
 	unsigned long pressure;
 
 	/*
+	 * This could happen, in such a case, when reclaiming ends by fatal
+	 * signal in shrink_inactive_list(). In this case, return
+	 * VMPRESSURE_LOW not to have userland miss reclaim activity.
+	 */
+	if (reclaimed > scanned)
+		return VMPRESSURE_LOW;
+
+	/*
 	 * We calculate the ratio (in percents) of how many pages were
 	 * scanned vs. reclaimed in a given time frame (window). Note that
 	 * time is in VM reclaimer's "ticks", i.e. number of pages
-- 
1.7.9.5


--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>