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Subject[PATCH 05/12] mm, slub: lower the default slub_max_order with CONFIG_SLUB_TINY
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With CONFIG_SLUB_TINY we want to minimize memory overhead. By lowering
the default slub_max_order we can make slab allocations use smaller
pages. However depending on object sizes, order-0 might not be the best
due to increased fragmentation. When testing on a 8MB RAM k210 system by
Damien Le Moal [1], slub_max_order=1 had the best results, so use that
as the default for CONFIG_SLUB_TINY.

[1] https://lore.kernel.org/all/6a1883c4-4c3f-545a-90e8-2cd805bcf4ae@opensource.wdc.com/

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/slub.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index 917b79278bad..bf726dd00f7d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3888,7 +3888,8 @@ EXPORT_SYMBOL(kmem_cache_alloc_bulk);
* take the list_lock.
*/
static unsigned int slub_min_order;
-static unsigned int slub_max_order = PAGE_ALLOC_COSTLY_ORDER;
+static unsigned int slub_max_order =
+ IS_ENABLED(CONFIG_SLUB_TINY) ? 1 : PAGE_ALLOC_COSTLY_ORDER;
static unsigned int slub_min_objects;

/*
--
2.38.1
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