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authorDavid Gibson <david@gibson.dropbear.id.au>2006-04-28 15:02:51 +1000
committerPaul Mackerras <paulus@samba.org>2006-04-28 15:02:51 +1000
commitf10a04c034c7285a1b15dfa4a83d3e56578e34e8 (patch)
treeee6bd0c670b6606017cbd88b56a1247ff241e00e /arch/powerpc/mm/init_64.c
parent37e53db8aa233c65142d63b496277bf5be9c0ade (diff)
[PATCH] powerpc: Fix pagetable bloat for hugepages
At present, ARCH=powerpc kernels can waste considerable space in pagetables when making large hugepage mappings. Hugepage PTEs go in PMD pages, but each PMD page maps 256M and so contains only 16 hugepage PTEs (128 bytes of data), but takes up a 1024 byte allocation. With CONFIG_PPC_64K_PAGES enabled (64k base page size), the situation is worse. Now hugepage PTEs are at the PTE page level (also mapping 256M), so we store 16 hugepage PTEs in a 64k allocation. The PowerPC MMU already means that any 256M region is either all hugepage, or all normal pages. Thus, with some care, we can use a different allocation for the hugepage PTE tables and only allocate the 128 bytes necessary. Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/mm/init_64.c')
-rw-r--r--arch/powerpc/mm/init_64.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
index babebd15bdc..9e30f968c18 100644
--- a/arch/powerpc/mm/init_64.c
+++ b/arch/powerpc/mm/init_64.c
@@ -162,7 +162,14 @@ static const char *pgtable_cache_name[ARRAY_SIZE(pgtable_cache_size)] = {
};
#endif /* CONFIG_PPC_64K_PAGES */
+#ifdef CONFIG_HUGETLB_PAGE
+/* Hugepages need one extra cache, initialized in hugetlbpage.c. We
+ * can't put into the tables above, because HPAGE_SHIFT is not compile
+ * time constant. */
+kmem_cache_t *pgtable_cache[ARRAY_SIZE(pgtable_cache_size)+1];
+#else
kmem_cache_t *pgtable_cache[ARRAY_SIZE(pgtable_cache_size)];
+#endif
void pgtable_cache_init(void)
{