On 06/22/2016 04:04 PM, Vlastimil Babka wrote:
On 06/21/2016 04:15 PM, Mel Gorman wrote:
This patch makes reclaim decisions on a per-node basis. A reclaimer knows
what zone is required by the allocation request and skips pages from
higher zones. In many cases this will be ok because it's a GFP_HIGHMEM
request of some description. On 64-bit, ZONE_DMA32 requests will cause
some problems but 32-bit devices on 64-bit platforms are increasingly
rare. Historically it would have been a major problem on 32-bit with big
Highmem:Lowmem ratios but such configurations are also now rare and even
where they exist, they are not encouraged. If it really becomes a problem,
it'll manifest as very low reclaim efficiencies.
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
[...]
@@ -2540,14 +2559,14 @@ static inline bool compaction_ready(struct zone *zone, int order, int classzone_
* If a zone is deemed to be full of pinned pages then just give it a light
* scan then give up on it.
*/
-static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
+static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc,
+ enum zone_type classzone_idx)
{
struct zoneref *z;
struct zone *zone;
unsigned long nr_soft_reclaimed;
unsigned long nr_soft_scanned;
gfp_t orig_mask;
- enum zone_type requested_highidx = gfp_zone(sc->gfp_mask);
/*
* If the number of buffer_heads in the machine exceeds the maximum
@@ -2560,15 +2579,20 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
for_each_zone_zonelist_nodemask(zone, z, zonelist,
gfp_zone(sc->gfp_mask), sc->nodemask) {
Using sc->reclaim_idx could be faster/nicer here than gfp_zone()?
Although after "mm, vmscan: Update classzone_idx if buffer_heads_over_limit"
there would need to be a variable for the highmem adjusted value - maybe reuse
"requested_highidx"? Not important though.
- enum zone_type classzone_idx;
-
if (!populated_zone(zone))
continue;
- classzone_idx = requested_highidx;
+ /*
+ * Note that reclaim_idx does not change as it is the highest
+ * zone reclaimed from which for empty zones is a no-op but
+ * classzone_idx is used by shrink_node to test if the slabs
+ * should be shrunk on a given node.
+ */
while (!populated_zone(zone->zone_pgdat->node_zones +
- classzone_idx))
+ classzone_idx)) {
classzone_idx--;
+ continue;
Oh and Michal's comment on Patch 20 made me realize that my objection to v6
about possible underflow of sc->reclaim_idx and classzone_idx seems to still
apply here for classzone_idx? Updated example: Normal zone allocation. A small
node 0 without Normal zone will get us classzone_idx == dma32. Node 1 next in
zonelist won't have dma/dma32 zones so we won't see node_zones + classzone_idx
populated, and the while loop will lead to underflow of classzone_idx.
I may be missing something, but I don't really see another way around it than
resetting classzone_idx to sc->reclaim_idx before the while loop.
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