Rohit, Seth wrote:
the only changes in this clean up are:
Looking good. I imagine it must be good for icache.
Man, the page allocator somehow turned unreadable since I last
looked at it! We will want this patch.
1- remove the initial direct reclaim logic
2- GFP_HIGH pages are allowed to go little below low watermark sooner
I don't think #2 is any good. The reason we don't check GFP_HIGH on
the first time round is because we simply want to kick kswapd at its
normal watermark - ie. it doesn't matter what kind of allocation this
is, kswapd should start at the same time no matter what.
If you don't do this, then a GFP_HIGH allocator can allocate right
down to its limit before it kicks kswapd, then it either will fail or
will have to do direct reclaim.
I would be inclined to simply add a int gfp_high argument to
get_page_from_freelist, which would also somewhat match zone_watermark_ok.
3- Search for free pages unconditionally after direct reclaim
I've not added the logic of looking into PCPs first in this rev of patch. I will send a
seperate patch for adding that support (needing extra logic for NUMA).
Signed-off-by: Rohit Seth <[email protected]>
One other comment below:
+
+static struct page *
+get_page_from_freelist(unsigned int __nocast gfp_mask, unsigned int order,
+ struct zone **zones, int can_try_harder)
+{
+ struct zone *z;
+ struct page *page = NULL;
+ int classzone_idx = zone_idx(zones[0]);
+ int i;
+
+ /*
+ * Go through the zonelist once, looking for a zone with enough free.
+ * See also cpuset_zone_allowed() comment in kernel/cpuset.c.
+ */
+ for (i = 0; (z = zones[i]) != NULL; i++) {
+ if (!cpuset_zone_allowed(z, gfp_mask))
+ continue;
+
+ if ((can_try_harder >= 0) &&
+ (!zone_watermark_ok(z, order, z->pages_low,
+ classzone_idx, can_try_harder,
+ gfp_mask & __GFP_HIGH)))
+ continue;
+
+ page = buffered_rmqueue(z, order, gfp_mask, 1);
+ if (page)
+ break;
+ }
+ return page;
+}
[snip]
@@ -968,7 +931,7 @@
}
return NULL;
got_pg:
- zone_statistics(zonelist, z);
+ zone_statistics(zonelist, page_zone(page));
return page;
How about moving the zone_statistics up into the 'if (page)'
test of get_page_from_freelist? This way we don't have to
evaluate page_zone().
--
SUSE Labs, Novell Inc.
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