Re: [PATCH 2.6.17-rc1-mm1 6/6] Migrate-on-fault - add MPOL_NOOP

[Lee Schermerhorn <Lee.Schermerhorn@hp.com>]

Migrate-on-fault prototype 6/6 V0.2 - add MPOL_NOOP

V0.2 -	this patch is new in the V0.2 series.  No change between
	2.6.16-mm1 and 2.6.17-rc1-mm1

This patch augments the MPOL_MF_LAZY feature by adding a "NOOP"
policy to mbind().  When the NOOP policy is used with the 'MOVE
and 'LAZY flags, mbind() [check_range()] will walk the specified
range and unmap eligible pages so that they will be migrated on
next touch.

Signed-off-by:  Lee Schermerhorn <lee.schermerhorn@hp.com>

Index: linux-2.6.16-mm1/include/linux/mempolicy.h
===================================================================
--- linux-2.6.16-mm1.orig/include/linux/mempolicy.h	2006-03-23 16:49:16.000000000 -0500
+++ linux-2.6.16-mm1/include/linux/mempolicy.h	2006-03-23 16:49:22.000000000 -0500
@@ -13,8 +13,9 @@
 #define MPOL_PREFERRED	1
 #define MPOL_BIND	2
 #define MPOL_INTERLEAVE	3
+#define MPOL_NOOP	4	/* retain existing policy for range */
 
-#define MPOL_MAX MPOL_INTERLEAVE
+#define MPOL_MAX MPOL_NOOP
 
 /* Flags for get_mem_policy */
 #define MPOL_F_NODE	(1<<0)	/* return next IL mode instead of node mask */
Index: linux-2.6.16-mm1/mm/mempolicy.c
===================================================================
--- linux-2.6.16-mm1.orig/mm/mempolicy.c	2006-03-23 16:49:16.000000000 -0500
+++ linux-2.6.16-mm1/mm/mempolicy.c	2006-03-23 16:49:22.000000000 -0500
@@ -117,6 +117,7 @@ static int mpol_check_policy(int mode, n
 
 	switch (mode) {
 	case MPOL_DEFAULT:
+	case MPOL_NOOP:
 		if (!empty)
 			return -EINVAL;
 		break;
@@ -163,7 +164,7 @@ static struct mempolicy *mpol_new(int mo
 	struct mempolicy *policy;
 
 	PDprintk("setting mode %d nodes[0] %lx\n", mode, nodes_addr(*nodes)[0]);
-	if (mode == MPOL_DEFAULT)
+	if (mode == MPOL_DEFAULT || mode == MPOL_NOOP)
 		return NULL;
 	policy = kmem_cache_alloc(policy_cache, GFP_KERNEL);
 	if (!policy)
@@ -726,7 +727,7 @@ long do_mbind(unsigned long start, unsig
 	if (start & ~PAGE_MASK)
 		return -EINVAL;
 
-	if (mode == MPOL_DEFAULT)
+	if (mode == MPOL_DEFAULT || mode == MPOL_NOOP)
 		flags &= ~MPOL_MF_STRICT;
 
 	len = (len + PAGE_SIZE - 1) & PAGE_MASK;
@@ -762,10 +763,13 @@ long do_mbind(unsigned long start, unsig
 	if (!IS_ERR(vma)) {
 		int nr_failed = 0;
 
-		err = mbind_range(vma, start, end, new);
+		if (mode == MPOL_NOOP)
+			err = 0;
+		else
+			err = mbind_range(vma, start, end, new);
 
 		if (!list_empty(&pagelist)) {
-			if (!(flags & MPOL_MF_LAZY))
+			if (mode != MPOL_NOOP && !(flags & MPOL_MF_LAZY))
 				nr_failed = migrate_pages_to(&pagelist,
 								 vma, -1);
 			else


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