On 09/30/2015 10:46 AM, Mel Gorman wrote:
On Tue, Sep 29, 2015 at 02:05:07PM -0700, Andrew Morton wrote:
The wizard of oz because because!
This should fix it up better than clicking my shoes three times.
---8<---
From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: [PATCH] mm, page_alloc: only enforce watermarks for order-0
allocations -fix
This patch is updating comments for clarity and converts a bool to an
int. The code as-is is ok as the compiler is meant to cast it correctly
but it looks odd to people who know the value would be truncated and
lost for other types.
This is a fix to the mmotm patch
mm-page_alloc-only-enforce-watermarks-for-order-0-allocations.patch
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Ack (with nitpick below)
---
mm/page_alloc.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 25731624d734..fedec98aafca 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2332,7 +2332,7 @@ static bool __zone_watermark_ok(struct zone *z, unsigned int order,
{
long min = mark;
int o;
- const bool alloc_harder = (alloc_flags & ALLOC_HARDER);
+ const int alloc_harder = (alloc_flags & ALLOC_HARDER);
How bout the !!(alloc_flags & ALLOC_HARDER) conversion to bool? Unless
it forces to make the compiler some extra work...
/* free_pages may go negative - that's OK */
free_pages -= (1 << order) - 1;
@@ -2356,14 +2356,19 @@ static bool __zone_watermark_ok(struct zone *z, unsigned int order,
free_pages -= zone_page_state(z, NR_FREE_CMA_PAGES);
#endif
+ /*
+ * 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;
- /* order-0 watermarks are ok */
+ /* If this is an order-0 request then the watermark is fine */
if (!order)
return true;
- /* Check at least one high-order page is free */
+ /* 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;
--
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