From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
Let us look at the series of scenarios below with WMARK_LOW=25MB,WMARK_MIN=5MB
(managed pages 1.9GB). We can know that current 'fixed 1/2 ratio' start to use
CMA since C which actually has caused U&R lower than WMARK_LOW (this should be
deemed as against current memory policy, that is, U&R should either stay around
WATERMARK_LOW when no allocation or do reclaim via enter slowpath)
free_cma/free_pages(MB) A(12/30) B(12/25) C(12/20)
fixed 1/2 ratio N N Y
this commit Y Y Y
Suggested-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
v2: do proportion check when zone_watermark_ok, update commit message
---
---
mm/page_alloc.c | 36 ++++++++++++++++++++++++++++++++----
1 file changed, 32 insertions(+), 4 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0745aed..d0baeab 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3071,6 +3071,34 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
}
+#ifdef CONFIG_CMA
+static bool __if_use_cma_first(struct zone *zone, unsigned int order, unsigned int alloc_flags)
+{
+ unsigned long cma_proportion = 0;
+ unsigned long cma_free_proportion = 0;
+ unsigned long watermark = 0;
+ long count = 0;
+ bool cma_first = false;
+
+ watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
+ /*check if GFP_MOVABLE pass previous watermark check via the help of CMA*/
+ if (!zone_watermark_ok(zone, order, watermark, 0, alloc_flags & (~ALLOC_CMA)))
+ /* WMARK_LOW failed lead to using cma first, this helps U&R stay
+ * around low when being drained by GFP_MOVABLE
+ */
+ cma_first = true;
+ else {
+ /*check proportion when zone_watermark_ok*/
+ count = atomic_long_read(&zone->managed_pages);
+ cma_proportion = zone->cma_pages * 100 / count;
+ cma_free_proportion = zone_page_state(zone, NR_FREE_CMA_PAGES) * 100
+ / zone_page_state(zone, NR_FREE_PAGES);
+ cma_first = (cma_free_proportion >= cma_proportion * 2
+ || cma_free_proportion >= 50);
+ }
+ return cma_first;
+}
+#endif
/*
* Do the hard work of removing an element from the buddy allocator.
* Call me with the zone->lock already held.
@@ -3087,10 +3115,10 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
* allocating from CMA when over half of the zone's free memory
* is in the CMA area.
*/
- if (alloc_flags & ALLOC_CMA &&
- zone_page_state(zone, NR_FREE_CMA_PAGES) >
- zone_page_state(zone, NR_FREE_PAGES) / 2) {
- page = __rmqueue_cma_fallback(zone, order);
+ if (migratetype == MIGRATE_MOVABLE) {
+ bool cma_first = __if_use_cma_first(zone, order, alloc_flags);
+
+ page = cma_first ? __rmqueue_cma_fallback(zone, order) : NULL;
if (page)
return page;
}
--
1.9.1
