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Message-ID: <Pine.LNX.4.64.0710021732520.32678@schroedinger.engr.sgi.com>
Date: Tue, 2 Oct 2007 17:37:34 -0700 (PDT)
From: Christoph Lameter <clameter@....com>
To: Mel Gorman <mel@....ul.ie>
cc: Hugh Dickins <hugh@...itas.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: kswapd min order, slub max order [was Re: -mm merge plans for
2.6.24]
On Tue, 2 Oct 2007, Christoph Lameter wrote:
> The maximum order of allocation used by SLUB may have to depend on the
> number of page structs in the system since small systems (128M was the
> case that Peter found) can easier get into trouble. SLAB has similar
> measures to avoid order 1 allocations for small systems below 32M.
A patch like this? This is based on the number of page structs on the
system. Maybe it needs to be based on the number of MAX_ORDER blocks
for antifrag?
SLUB: Determine slub_max_order depending on the number of pages available
Determine the maximum order to be used for slabs and the mininum
desired number of objects in a slab from the amount of pages that
a system has available (like SLAB does for the order 1/0 distinction).
For systems with less than 128M only use order 0 allocations (SLAB does
that for <32M only). The order 0 config is useful for small systems to
minimize the memory used. Memory easily fragments since we have less than
32k pages to play with. Order 0 insures that higher order allocations are
minimized (Larger orders must still be used for objects that do not fit
into order 0 pages).
Then step up to order 1 for systems < 256000 pages (1G)
Order 2 limit to systems < 1000000 page structs (4G)
Order 3 for systems larger than that.
Signed-off-by: Christoph Lameter <clameter@....com>
---
mm/slub.c | 49 +++++++++++++++++++++++++------------------------
1 file changed, 25 insertions(+), 24 deletions(-)
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c 2007-10-02 09:26:16.000000000 -0700
+++ linux-2.6/mm/slub.c 2007-10-02 16:40:22.000000000 -0700
@@ -153,25 +153,6 @@ static inline void ClearSlabDebug(struct
/* Enable to test recovery from slab corruption on boot */
#undef SLUB_RESILIENCY_TEST
-#if PAGE_SHIFT <= 12
-
-/*
- * Small page size. Make sure that we do not fragment memory
- */
-#define DEFAULT_MAX_ORDER 1
-#define DEFAULT_MIN_OBJECTS 4
-
-#else
-
-/*
- * Large page machines are customarily able to handle larger
- * page orders.
- */
-#define DEFAULT_MAX_ORDER 2
-#define DEFAULT_MIN_OBJECTS 8
-
-#endif
-
/*
* Mininum number of partial slabs. These will be left on the partial
* lists even if they are empty. kmem_cache_shrink may reclaim them.
@@ -1718,8 +1699,9 @@ static struct page *get_object_page(cons
* take the list_lock.
*/
static int slub_min_order;
-static int slub_max_order = DEFAULT_MAX_ORDER;
-static int slub_min_objects = DEFAULT_MIN_OBJECTS;
+static int slub_max_order;
+static int slub_min_objects = 4;
+static int manual;
/*
* Merge control. If this is set then no merging of slab caches will occur.
@@ -2237,7 +2219,7 @@ static struct kmem_cache *kmalloc_caches
static int __init setup_slub_min_order(char *str)
{
get_option (&str, &slub_min_order);
-
+ manual = 1;
return 1;
}
@@ -2246,7 +2228,7 @@ __setup("slub_min_order=", setup_slub_mi
static int __init setup_slub_max_order(char *str)
{
get_option (&str, &slub_max_order);
-
+ manual = 1;
return 1;
}
@@ -2255,7 +2237,7 @@ __setup("slub_max_order=", setup_slub_ma
static int __init setup_slub_min_objects(char *str)
{
get_option (&str, &slub_min_objects);
-
+ manual = 1;
return 1;
}
@@ -2566,6 +2548,16 @@ int kmem_cache_shrink(struct kmem_cache
}
EXPORT_SYMBOL(kmem_cache_shrink);
+/*
+ * Table to autotune the maximum slab order based on the number of pages
+ * that the system has available.
+ */
+static unsigned long __initdata phys_pages_for_order[PAGE_ALLOC_COSTLY_ORDER] = {
+ 32768, /* >128M if using 4K pages, >512M (16k), >2G (64k) */
+ 256000, /* >1G if using 4k pages, >4G (16k), >16G (64k) */
+ 1000000 /* >4G if using 4k pages, >16G (16k), >64G (64k) */
+};
+
/********************************************************************
* Basic setup of slabs
*******************************************************************/
@@ -2575,6 +2567,15 @@ void __init kmem_cache_init(void)
int i;
int caches = 0;
+ if (!manual) {
+ /* No manual parameters. Autotune for system */
+ for (i = 0; i < PAGE_ALLOC_COSTLY_ORDER; i++)
+ if (num_physpages > phys_pages_for_order[i]) {
+ slub_max_order++;
+ slub_min_objects <<= 1;
+ }
+ }
+
#ifdef CONFIG_NUMA
/*
* Must first have the slab cache available for the allocations of the
-
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