[PATCH v3] tmpfs not interleaving properly

[Nathan Zimmer <nzimmer@sgi.com>]

When tmpfs has the memory policy interleaved it always starts allocating at each
file at node 0.  When there are many small files the lower nodes fill up
disproportionately.
This patch attempts to spread out node usage by starting files at nodes other
then 0.  I disturbed the addr parameter since alloc_pages_vma will only use it
when the policy is MPOL_INTERLEAVE.  A files preferred node is selected by 
the cpu_mem_spread_node rotor.

v2: passed preferred node via addr
v3: using current->cpuset_mem_spread_rotor instead of random_node

Cc: Christoph Lameter <cl@linux.com>
Cc: Nick Piggin <npiggin@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Nathan T Zimmer <nzimmer@sgi.com>
---

 include/linux/shmem_fs.h |    1 +
 mm/shmem.c               |    9 +++++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index bef2cf0..cfe8a34 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -17,6 +17,7 @@ struct shmem_inode_info {
 		char		*symlink;	/* unswappable short symlink */
 	};
 	struct shared_policy	policy;		/* NUMA memory alloc policy */
+	unsigned long           node_offset;	/* bias for interleaved nodes */
 	struct list_head	swaplist;	/* chain of maybes on swap */
 	struct list_head	xattr_list;	/* list of shmem_xattr */
 	struct inode		vfs_inode;
diff --git a/mm/shmem.c b/mm/shmem.c
index a15a466..93801b3 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -64,6 +64,7 @@ static struct vfsmount *shm_mnt;
 #include <linux/highmem.h>
 #include <linux/seq_file.h>
 #include <linux/magic.h>
+#include <linux/cpuset.h>
 
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -938,9 +939,12 @@ static struct page *shmem_alloc_page(gfp_t gfp,
 	pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 
 	/*
-	 * alloc_page_vma() will drop the shared policy reference
+	 * alloc_page_vma() will drop the shared policy reference.
+	 *
+	 * To avoid allocating all tmpfs pages on node 0, we fake up a virtual
+	 * address based on this file's predetermined preferred node.
 	 */
-	return alloc_page_vma(gfp, &pvma, 0);
+	return alloc_page_vma(gfp, &pvma, info->node_offset << PAGE_SHIFT);
 }
 #else /* !CONFIG_NUMA */
 #ifdef CONFIG_TMPFS
@@ -1374,6 +1378,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
 			inode->i_fop = &shmem_file_operations;
 			mpol_shared_policy_init(&info->policy,
 						 shmem_get_sbmpol(sbinfo));
+			info->node_offset = cpuset_mem_spread_node();
 			break;
 		case S_IFDIR:
 			inc_nlink(inode);

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