Re: [PATCH 3/7] Allow CONFIG_MIGRATION to be set without CONFIG_NUMA
From: Mel Gorman
Date: Tue May 29 2007 - 14:21:53 EST
On Tue, 29 May 2007, Christoph Lameter wrote:
On Tue, 29 May 2007, Mel Gorman wrote:
CONFIG_MIGRATION currently depends on CONFIG_NUMA. move_pages() is the only
user of migration today and as this system call is only meaningful on NUMA,
it makes sense. However, memory compaction will operate within a zone and is
useful on both NUMA and non-NUMA systems. This patch allows CONFIG_MIGRATION
to be used in all memory models. To preserve existing behaviour, move_pages()
is only available when CONFIG_NUMA is set.
Hmmm... I thought I had this already set up so that it would be easy to
switch page migration to not depend on CONFIG_NUMA. Not so it seems.
It's only policy_zone that it got hung-up on. In an earlir version, I just
defined policy_zone outside of mempolicy but it was messy looking.
--- linux-2.6.22-rc2-mm1-005_migrate_nocontext/include/linux/migrate.h 2007-05-28 14:11:32.000000000 +0100
+++ linux-2.6.22-rc2-mm1-015_migration_flatmem/include/linux/migrate.h 2007-05-29 10:00:09.000000000 +0100
@@ -7,7 +7,7 @@
typedef struct page *new_page_t(struct page *, unsigned long private, int **);
-#ifdef CONFIG_MIGRATION
+#ifdef CONFIG_SYSCALL_MOVE_PAGES
/* Check if a vma is migratable */
static inline int vma_migratable(struct vm_area_struct *vma)
{
@@ -24,7 +24,14 @@ static inline int vma_migratable(struct
return 0;
return 1;
}
+#else
+static inline int vma_migratable(struct vm_area_struct *vma)
+{
+ return 0;
+}
+#endif
I guess we get compilation failures because of the reference to
policy_zone here for the !NUMA case? I think vma migratable is not used at
all if !NUMA.
It isn't that I could tell.
+#ifdef CONFIG_MIGRATION
extern int isolate_lru_page(struct page *p, struct list_head *pagelist);
extern int putback_lru_pages(struct list_head *l);
extern int migrate_page(struct address_space *,
@@ -40,8 +47,6 @@ extern int migrate_vmas(struct mm_struct
const nodemask_t *from, const nodemask_t *to,
unsigned long flags);
#else
-static inline int vma_migratable(struct vm_area_struct *vma)
- { return 0; }
Maybe this block is not necessary?
Agreed. For a long time I didn't have it included at all but put it back
in to preserve existing behaviour. I'll remove it.
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.22-rc2-mm1-005_migrate_nocontext/include/linux/mm.h linux-2.6.22-rc2-mm1-015_migration_flatmem/include/linux/mm.h
--- linux-2.6.22-rc2-mm1-005_migrate_nocontext/include/linux/mm.h 2007-05-24 10:13:34.000000000 +0100
+++ linux-2.6.22-rc2-mm1-015_migration_flatmem/include/linux/mm.h 2007-05-28 14:13:44.000000000 +0100
@@ -242,6 +242,8 @@ struct vm_operations_struct {
int (*set_policy)(struct vm_area_struct *vma, struct mempolicy *new);
struct mempolicy *(*get_policy)(struct vm_area_struct *vma,
unsigned long addr);
+#endif /* CONFIG_NUMA */
+#ifdef CONFIG_MIGRATION
int (*migrate)(struct vm_area_struct *vma, const nodemask_t *from,
const nodemask_t *to, unsigned long flags);
#endif
Correct.
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.22-rc2-mm1-005_migrate_nocontext/mm/Kconfig linux-2.6.22-rc2-mm1-015_migration_flatmem/mm/Kconfig
--- linux-2.6.22-rc2-mm1-005_migrate_nocontext/mm/Kconfig 2007-05-24 10:13:34.000000000 +0100
+++ linux-2.6.22-rc2-mm1-015_migration_flatmem/mm/Kconfig 2007-05-29 09:57:23.000000000 +0100
@@ -145,13 +145,16 @@ config SPLIT_PTLOCK_CPUS
config MIGRATION
bool "Page migration"
def_bool y
- depends on NUMA
help
Allows the migration of the physical location of pages of processes
while the virtual addresses are not changed. This is useful for
example on NUMA systems to put pages nearer to the processors accessing
the page.
+config SYSCALL_MOVE_PAGES
+ def_bool y
+ depends on MIGRATION && NUMA
+
Do we really need the CONFIG_SYSCALL_MOVE_PAGES? I think you will directly
access the lower levels. So why have it? CONFIG_SYSCALL_MOVE_PAGES ==
CONFIG_NUMA.
Without SYSCALL_MOVE_PAGES, the check in migrate.h becomes
#if defined(CONFIG_NUMA) && defined(CONFIG_MIGRATION)
/* Check if a vma is migratable */
static inline int vma_migratable(struct vm_area_struct *vma)
#endif
That in itself is fine but in mm/migrate.c I didn't want to define
sys_move_pages() in the non-NUMA case. Whatever about the header file
where SYSCALL_MOVE_PAGES obscures understanding, I think it makes sense to
have SYSCALL_MOVE_PAGES for mm/migrate.c . What do you think?
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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