On Mon 05-01-15 18:17:40, Vlastimil Babka wrote:
> The function prep_new_page() sets almost everything in the struct page of the
> page being allocated, except page->pfmemalloc. This is not obvious and has at
> least once led to a bug where page->pfmemalloc was forgotten to be set
> correctly, see commit 8fb74b9fb2b1 ("mm: compaction: partially revert capture
> of suitable high-order page").
>
> This patch moves the pfmemalloc setting to prep_new_page(), which means it
> needs to gain alloc_flags parameter. The call to prep_new_page is moved from
> buffered_rmqueue() to get_page_from_freelist(), which also leads to simpler
> code. An obsolete comment for buffered_rmqueue() is replaced.
>
> In addition to better maintainability there is a small reduction of code and
> stack usage for get_page_from_freelist(), which inlines the other functions
> involved.
>
> add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-145 (-145)
> function old new delta
> get_page_from_freelist 2670 2525 -145
>
> Stack usage is reduced from 184 to 168 bytes.
>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxx>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxx>
get_page_from_freelist has grown too hairy. I agree that it is tiny less
confusing now because we are not breaking out of the loop in the
successful case.
Acked-by: Michal Hocko <mhocko@xxxxxxx>
[...]
> @@ -2177,25 +2181,16 @@ zonelist_scan:
> try_this_zone:
> page = buffered_rmqueue(preferred_zone, zone, order,
> gfp_mask, migratetype);
> - if (page)
> - break;
> + if (page) {
> + if (prep_new_page(page, order, gfp_mask, alloc_flags))
> + goto try_this_zone;
> + return page;
> + }
I would probably liked `do {} while ()' more because it wouldn't use the
goto, but this is up to you:
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1bb65e6f48dd..1682d766cb8e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2175,10 +2175,11 @@ zonelist_scan:
}
try_this_zone:
- page = buffered_rmqueue(preferred_zone, zone, order,
+ do {
+ page = buffered_rmqueue(preferred_zone, zone, order,
gfp_mask, migratetype);
- if (page)
- break;
+ } while (page && prep_new_page(page, order, gfp_mask,
+ alloc_flags));
this_zone_full:
if (IS_ENABLED(CONFIG_NUMA) && zlc_active)
zlc_mark_zone_full(zonelist, z);
[...]
--
Michal Hocko
SUSE Labs
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