Re: [PATCH 2.6.17-rc1-mm1 8/9] AutoPage Migration - V0.2 - add max mapcount migration threshold

Lee Schermerhorn
2006-04-07T20:42:28Z

AutoPage Migration - V0.2 - 8/9 add max mapcount migration threshold

This patch adds an additional migration control that allows one
to vary the page mapcount threshold above which pages will not
be migrated by MPOL_MF_MOVE. The default value is 1, which yields
the same behavior as before this patch.

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

Index: linux-2.6.16-mm1/include/linux/auto-migrate.h
===================================================================
--- linux-2.6.16-mm1.orig/include/linux/auto-migrate.h 2006-03-23 16:50:24.000000000 -0500
+++ linux-2.6.16-mm1/include/linux/auto-migrate.h 2006-03-23 16:50:30.000000000 -0500
@@ -20,6 +20,8 @@ extern unsigned long auto_migrate_interv
#define AUTO_MIGRATE_INTERVAL_MIN (5*HZ)
#define AUTO_MIGRATE_INTERVAL_MAX (300*HZ)

+extern unsigned int migrate_max_mapcount;
+
#ifdef _LINUX_SCHED_H /* only used where this is defined */
static inline void check_internode_migration(task_t *task, int dest_cpu)
{
@@ -98,6 +100,7 @@ out:
#define too_soon_for_internode_migration(t,c) 0

#define check_migrate_pending() /* NOTHING */
+#define migrate_max_mapcount (1)

#endif /* CONFIG_MIGRATION */

Index: linux-2.6.16-mm1/mm/migrate.c
===================================================================
--- linux-2.6.16-mm1.orig/mm/migrate.c 2006-03-23 16:50:24.000000000 -0500
+++ linux-2.6.16-mm1/mm/migrate.c 2006-03-23 16:50:30.000000000 -0500
@@ -107,12 +107,35 @@ static ssize_t auto_migrate_interval_sto
}
MIGRATION_ATTR_RW(auto_migrate_interval);

+/*
+ * migrate_max_mapcount: specify how many mappers allowed
+ * before we won't migrate a page via MPOL_MF_MOVE.
+ */
+unsigned int migrate_max_mapcount = 1; /* default == minimum */
+
+static ssize_t migrate_max_mapcount_show(struct subsystem *subsys, char *page)
+{
+ return sprintf(page, "migrate_max_mapcount %d\n", migrate_max_mapcount);
+}
+static ssize_t migrate_max_mapcount_store(struct subsystem *subsys,
+ const char *page, size_t count)
+{
+ unsigned int n = simple_strtoul(page, NULL, 10);
+ if (n < 1)
+ migrate_max_mapcount = 1;
+ else
+ migrate_max_mapcount = n;
+ return count;
+}
+MIGRATION_ATTR_RW(migrate_max_mapcount);
+
decl_subsys(migration, NULL, NULL);
EXPORT_SYMBOL(migration_subsys);

static struct attribute *migration_attrs[] = {
&auto_migrate_enable_attr.attr,
&auto_migrate_interval_attr.attr,
+ &migrate_max_mapcount_attr.attr,
NULL
};

Index: linux-2.6.16-mm1/mm/mempolicy.c
===================================================================
--- linux-2.6.16-mm1.orig/mm/mempolicy.c 2006-03-23 16:49:34.000000000 -0500
+++ linux-2.6.16-mm1/mm/mempolicy.c 2006-03-23 16:50:30.000000000 -0500
@@ -87,6 +87,7 @@
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <linux/migrate.h>
+#include <linux/auto-migrate.h>

#include <asm/tlbflush.h>
#include <asm/uaccess.h>
@@ -452,7 +453,6 @@ static int contextualize_policy(int mode
return mpol_check_policy(mode, nodes);
}

-
/*
* Update task->flags PF_MEMPOLICY bit: set iff non-default
* mempolicy. Allows more rapid checking of this (combined perhaps
@@ -611,9 +611,10 @@ static void migrate_page_add(struct page
unsigned long flags)
{
/*
- * Avoid migrating a page that is shared with others.
+ * Avoid migrating a page that is shared with [too many] others.
*/
- if ((flags & MPOL_MF_MOVE_ALL) || page_mapcount(page) == 1)
+ if ((flags & MPOL_MF_MOVE_ALL) ||
+ page_mapcount(page) <= migrate_max_mapcount)
isolate_lru_page(page, pagelist);