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-rw-r--r--mm/page_alloc.c53
1 files changed, 39 insertions, 14 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 55e9c56dfe54..b8d560afe266 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2322,8 +2322,10 @@ static inline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
#endif /* CONFIG_FAIL_PAGE_ALLOC */
/*
- * Return true if free pages are above 'mark'. This takes into account the order
- * of the allocation.
+ * Return true if free base pages are above 'mark'. For high-order checks it
+ * will return true of the order-0 watermark is reached and there is at least
+ * one free page of a suitable size. Checking now avoids taking the zone lock
+ * to check in the allocation paths if no pages are free.
*/
static bool __zone_watermark_ok(struct zone *z, unsigned int order,
unsigned long mark, int classzone_idx, int alloc_flags,
@@ -2331,7 +2333,7 @@ static bool __zone_watermark_ok(struct zone *z, unsigned int order,
{
long min = mark;
int o;
- long free_cma = 0;
+ const int alloc_harder = (alloc_flags & ALLOC_HARDER);
/* free_pages may go negative - that's OK */
free_pages -= (1 << order) - 1;
@@ -2344,7 +2346,7 @@ static bool __zone_watermark_ok(struct zone *z, unsigned int order,
* the high-atomic reserves. This will over-estimate the size of the
* atomic reserve but it avoids a search.
*/
- if (likely(!(alloc_flags & ALLOC_HARDER)))
+ if (likely(!alloc_harder))
free_pages -= z->nr_reserved_highatomic;
else
min -= min / 4;
@@ -2352,22 +2354,45 @@ static bool __zone_watermark_ok(struct zone *z, unsigned int order,
#ifdef CONFIG_CMA
/* If allocation can't use CMA areas don't use free CMA pages */
if (!(alloc_flags & ALLOC_CMA))
- free_cma = zone_page_state(z, NR_FREE_CMA_PAGES);
+ free_pages -= zone_page_state(z, NR_FREE_CMA_PAGES);
#endif
- if (free_pages - free_cma <= min + z->lowmem_reserve[classzone_idx])
+ /*
+ * Check watermarks for an order-0 allocation request. If these
+ * are not met, then a high-order request also cannot go ahead
+ * even if a suitable page happened to be free.
+ */
+ if (free_pages <= min + z->lowmem_reserve[classzone_idx])
return false;
- for (o = 0; o < order; o++) {
- /* At the next order, this order's pages become unavailable */
- free_pages -= z->free_area[o].nr_free << o;
- /* Require fewer higher order pages to be free */
- min >>= 1;
+ /* If this is an order-0 request then the watermark is fine */
+ if (!order)
+ return true;
+
+ /* For a high-order request, check at least one suitable page is free */
+ for (o = order; o < MAX_ORDER; o++) {
+ struct free_area *area = &z->free_area[o];
+ int mt;
+
+ if (!area->nr_free)
+ continue;
+
+ if (alloc_harder)
+ return true;
- if (free_pages <= min)
- return false;
+ for (mt = 0; mt < MIGRATE_PCPTYPES; mt++) {
+ if (!list_empty(&area->free_list[mt]))
+ return true;
+ }
+
+#ifdef CONFIG_CMA
+ if ((alloc_flags & ALLOC_CMA) &&
+ !list_empty(&area->free_list[MIGRATE_CMA])) {
+ return true;
+ }
+#endif
}
- return true;
+ return false;
}
bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,