On (10/05/07 15:49), Christoph Lameter didst pronounce:
> On Thu, 10 May 2007, Mel Gorman wrote:
>
> > > I cannot predict how allocations on a slab will be performed. In order
> > > to avoid the higher order allocations in we would have to add a flag
> > > that tells SLUB at slab creation creation time that this cache will be
> > > used for atomic allocs and thus we can avoid configuring slabs in such a
> > > way that they use higher order allocs.
> > >
> >
> > It is an option. I had the gfp flags passed in to kmem_cache_create() in
> > mind for determining this but SLUB creates slabs differently and different
> > flags could be passed into kmem_cache_alloc() of course.
>
> So we have a collection of flags to add
>
> SLAB_USES_ATOMIC
This is a possibility.
> SLAB_TEMPORARY
I have a patch for this sitting in a queue waiting for testing
> SLAB_PERSISTENT
> SLAB_RECLAIMABLE
> SLAB_MOVABLE
I don't think these are required because the necessary information is
available from the GFP flags.
>
> ?
>
> > Another alternative is that anti-frag used to also group high-order
> > allocations together and make it hard to fallback to those areas
> > for non-atomic allocations. It is currently backed out by the
> > patch dont-group-high-order-atomic-allocations.patch because
> > it was intended for rare high-order short-lived allocations
> > such as e1000 that are currently dealt with by MIGRATE_RESERVE
> > (bias-the-location-of-pages-freed-for-min_free_kbytes-in-the-same-max_order_nr_pages-blocks.patch)
> > The high-order atomic groupings may help here because the high-order
> > allocations are long-lived and would claim contiguous areas.
> >
> > The last alternative I think I mentioned already is to have the minimum
> > order kswapd reclaims as the same order SLUB uses instead of 0 so that
> > min_free_kbytes is kept at higher orders than current.
>
> Would you get a patch to Nicholas to test either of these solutions?
I do not have a kswapd related patch ready but the first alternative is
readily available.
Nicholas, could you backout the patch
dont-group-high-order-atomic-allocations.patch and test again please?
The following patch has the same effect. Thanks
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff
linux-2.6.21-mm2-clean/include/linux/mmzone.h
linux-2.6.21-mm2-grouphigh/include/linux/mmzone.h
--- linux-2.6.21-mm2-clean/include/linux/mmzone.h 2007-05-09
10:21:28.000000000 +0100
+++ linux-2.6.21-mm2-grouphigh/include/linux/mmzone.h 2007-05-10
23:54:45.000000000 +0100
@@ -38,8 +38,9 @@ extern int page_group_by_mobility_disabl
#define MIGRATE_UNMOVABLE 0
#define MIGRATE_RECLAIMABLE 1
#define MIGRATE_MOVABLE 2
-#define MIGRATE_RESERVE 3
-#define MIGRATE_TYPES 4
+#define MIGRATE_HIGHATOMIC 3
+#define MIGRATE_RESERVE 4
+#define MIGRATE_TYPES 5
#define for_each_migratetype_order(order, type) \
for (order = 0; order < MAX_ORDER; order++) \
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff
linux-2.6.21-mm2-clean/include/linux/pageblock-flags.h
linux-2.6.21-mm2-grouphigh/include/linux/pageblock-flags.h
--- linux-2.6.21-mm2-clean/include/linux/pageblock-flags.h 2007-05-09
10:21:28.000000000 +0100
+++ linux-2.6.21-mm2-grouphigh/include/linux/pageblock-flags.h 2007-05-10
23:54:45.000000000 +0100
@@ -31,7 +31,7 @@
/* Bit indices that affect a whole block of pages */
enum pageblock_bits {
- PB_range(PB_migrate, 2), /* 2 bits required for migrate types */
+ PB_range(PB_migrate, 3), /* 3 bits required for migrate types */
NR_PAGEBLOCK_BITS
};
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff
linux-2.6.21-mm2-clean/mm/page_alloc.c
linux-2.6.21-mm2-grouphigh/mm/page_alloc.c
--- linux-2.6.21-mm2-clean/mm/page_alloc.c 2007-05-09 10:21:28.000000000
+0100
+++ linux-2.6.21-mm2-grouphigh/mm/page_alloc.c 2007-05-10 23:54:45.000000000
+0100
@@ -167,6 +167,11 @@ static inline int allocflags_to_migratet
if (unlikely(page_group_by_mobility_disabled))
return MIGRATE_UNMOVABLE;
+ /* Cluster high-order atomic allocations together */
+ if (unlikely(order > 0) &&
+ (!(gfp_flags & __GFP_WAIT) || in_interrupt()))
+ return MIGRATE_HIGHATOMIC;
+
/* Cluster based on mobility */
return (((gfp_flags & __GFP_MOVABLE) != 0) << 1) |
((gfp_flags & __GFP_RECLAIMABLE) != 0);
@@ -713,10 +718,11 @@ static struct page *__rmqueue_smallest(s
* the free lists for the desirable migrate type are depleted
*/
static int fallbacks[MIGRATE_TYPES][MIGRATE_TYPES-1] = {
- [MIGRATE_UNMOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE,
MIGRATE_RESERVE },
- [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE, MIGRATE_MOVABLE,
MIGRATE_RESERVE },
- [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE,
MIGRATE_RESERVE },
- [MIGRATE_RESERVE] = { MIGRATE_RESERVE, MIGRATE_RESERVE,
MIGRATE_RESERVE }, /* Never used */
+ [MIGRATE_UNMOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE,
MIGRATE_HIGHATOMIC, MIGRATE_RESERVE },
+ [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE, MIGRATE_MOVABLE,
MIGRATE_HIGHATOMIC, MIGRATE_RESERVE },
+ [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE,
MIGRATE_HIGHATOMIC, MIGRATE_RESERVE },
+ [MIGRATE_HIGHATOMIC] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE,
MIGRATE_MOVABLE, MIGRATE_RESERVE },
+ [MIGRATE_RESERVE] = { MIGRATE_RESERVE, MIGRATE_RESERVE,
MIGRATE_RESERVE, MIGRATE_RESERVE }, /* Never used */
};
/*
@@ -810,7 +816,9 @@ static struct page *__rmqueue_fallback(s
int current_order;
struct page *page;
int migratetype, i;
+ int nonatomic_fallback_atomic = 0;
+retry:
/* Find the largest possible block of pages in the other list */
for (current_order = MAX_ORDER-1; current_order >= order;
--current_order) {
@@ -820,6 +828,14 @@ static struct page *__rmqueue_fallback(s
/* MIGRATE_RESERVE handled later if necessary */
if (migratetype == MIGRATE_RESERVE)
continue;
+ /*
+ * Make it hard to fallback to blocks used for
+ * high-order atomic allocations
+ */
+ if (migratetype == MIGRATE_HIGHATOMIC &&
+ start_migratetype != MIGRATE_UNMOVABLE &&
+ !nonatomic_fallback_atomic)
+ continue;
area = &(zone->free_area[current_order]);
if (list_empty(&area->free_list[migratetype]))
@@ -845,7 +861,8 @@ static struct page *__rmqueue_fallback(s
start_migratetype);
/* Claim the whole block if over half of it is
free */
- if ((pages << current_order) >= (1 <<
(MAX_ORDER-2)))
+ if ((pages << current_order) >= (1 <<
(MAX_ORDER-2)) &&
+ migratetype !=
MIGRATE_HIGHATOMIC)
set_pageblock_migratetype(page,
start_migratetype);
@@ -867,6 +884,12 @@ static struct page *__rmqueue_fallback(s
}
}
+ /* Allow fallback to high-order atomic blocks if memory is that low */
+ if (!nonatomic_fallback_atomic) {
+ nonatomic_fallback_atomic = 1;
+ goto retry;
+ }
+
/* Use MIGRATE_RESERVE rather than fail an allocation */
return __rmqueue_smallest(zone, order, MIGRATE_RESERVE);
}
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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