On Thu, Feb 15, 2018 at 09:49:00AM -0600, Christopher Lameter wrote:
> On Thu, 15 Feb 2018, Matthew Wilcox wrote:
>
> > What if ... on startup, slab allocated a MAX_ORDER page for itself.
> > It would then satisfy its own page allocation requests from this giant
> > page. If we start to run low on memory in the rest of the system, slab
> > can be induced to return some of it via its shrinker. If slab runs low
> > on memory, it tries to allocate another MAX_ORDER page for itself.
>
> The inducing of releasing memory back is not there but you can run SLUB
> with MAX_ORDER allocations by passing "slab_min_order=9" or so on bootup.
Maybe we should try this patch in order to automatically scale the slub
page size with the amount of memory in the machine?
diff --git a/mm/internal.h b/mm/internal.h
index e6bd35182dae..7059a8389194 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -167,6 +167,7 @@ extern void prep_compound_page(struct page *page, unsigned int order);
extern void post_alloc_hook(struct page *page, unsigned int order,
gfp_t gfp_flags);
extern int user_min_free_kbytes;
+extern unsigned long __meminitdata nr_kernel_pages;
#if defined CONFIG_COMPACTION || defined CONFIG_CMA
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ef9c259db041..3c51bb22403f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -264,7 +264,7 @@ int min_free_kbytes = 1024;
int user_min_free_kbytes = -1;
int watermark_scale_factor = 10;
-static unsigned long __meminitdata nr_kernel_pages;
+unsigned long __meminitdata nr_kernel_pages;
static unsigned long __meminitdata nr_all_pages;
static unsigned long __meminitdata dma_reserve;
diff --git a/mm/slub.c b/mm/slub.c
index e381728a3751..abca4a6e9b6c 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4194,6 +4194,23 @@ void __init kmem_cache_init(void)
if (debug_guardpage_minorder())
slub_max_order = 0;
+ if (slub_min_order == 0) {
+ unsigned long numentries = nr_kernel_pages;
+
+ /*
+ * Above 4GB, we start to care more about fragmenting large
+ * pages than about using the minimum amount of memory.
+ * Scale the slub page size at half the rate that we scale
+ * the memory size; at 4GB we double the page size to 8k,
+ * 16GB to 16k, 64GB to 32k, 256GB to 64k.
+ */
+ while (numentries > (4UL << 30)) {
+ if (slub_min_order >= slub_max_order)
+ break;
+ slub_min_order++;
+ numentries /= 4;
+ }
+ }
kmem_cache_node = &boot_kmem_cache_node;
kmem_cache = &boot_kmem_cache;
--
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