[PATCH] powerpc: 64k pages pmd alloc fix

This patch makes the kernel use a different kmem cache for PMD pages
as they are smaller than PTE pages. Avoids waste of memory.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/mm/init_64.c

@@ -20,6 +20,8 @@
  *
  */
 
+#undef DEBUG
+
 #include <linux/config.h>
 #include <linux/signal.h>
 #include <linux/sched.h>
@@ -64,6 +66,12 @@
 #include <asm/vdso.h>
 #include <asm/imalloc.h>
 
+#ifdef DEBUG
+#define DBG(fmt...) printk(fmt)
+#else
+#define DBG(fmt...)
+#endif
+
 #if PGTABLE_RANGE > USER_VSID_RANGE
 #warning Limited user VSID range means pagetable space is wasted
 #endif
@@ -188,14 +196,14 @@ static void zero_ctor(void *addr, kmem_cache_t *cache, unsigned long flags)
 }
 
 #ifdef CONFIG_PPC_64K_PAGES
-static const int pgtable_cache_size[2] = {
-	PTE_TABLE_SIZE, PGD_TABLE_SIZE
+static const unsigned int pgtable_cache_size[3] = {
+	PTE_TABLE_SIZE, PMD_TABLE_SIZE, PGD_TABLE_SIZE
 };
 static const char *pgtable_cache_name[ARRAY_SIZE(pgtable_cache_size)] = {
-	"pte_pmd_cache", "pgd_cache",
+	"pte_pmd_cache", "pmd_cache", "pgd_cache",
 };
 #else
-static const int pgtable_cache_size[2] = {
+static const unsigned int pgtable_cache_size[2] = {
 	PTE_TABLE_SIZE, PMD_TABLE_SIZE
 };
 static const char *pgtable_cache_name[ARRAY_SIZE(pgtable_cache_size)] = {
@@ -213,6 +221,8 @@ void pgtable_cache_init(void)
 		int size = pgtable_cache_size[i];
 		const char *name = pgtable_cache_name[i];
 
+		DBG("Allocating page table cache %s (#%d) "
+		    "for size: %08x...\n", name, i, size);
 		pgtable_cache[i] = kmem_cache_create(name,
 						     size, size,
 						     SLAB_HWCACHE_ALIGN |

include/asm-ppc64/pgalloc.h

@@ -10,8 +10,8 @@ extern kmem_cache_t *pgtable_cache[];
 
 #ifdef CONFIG_PPC_64K_PAGES
 #define PTE_CACHE_NUM	0
-#define PMD_CACHE_NUM	0
-#define PGD_CACHE_NUM	1
+#define PMD_CACHE_NUM	1
+#define PGD_CACHE_NUM	2
 #else
 #define PTE_CACHE_NUM	0
 #define PMD_CACHE_NUM	1