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| author | Lee Schermerhorn <Lee.Schermerhorn@hp.com> | 2006-04-22 11:35:48 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-04-22 18:19:52 +0200 |
| commit | 304dbdb7a4fbb7f40a6ad5c5836fdd456c233c63 (patch) | |
| tree | 2bdd71bb0ab19422362e9d3999f975ae27206965 /mm/shmem.c | |
| parent | [PATCH] x86_64: sparsemem does not need node_mem_map (diff) | |
| download | linux-304dbdb7a4fbb7f40a6ad5c5836fdd456c233c63.tar.xz linux-304dbdb7a4fbb7f40a6ad5c5836fdd456c233c63.zip | |
[PATCH] add migratepage address space op to shmem
Basic problem: pages of a shared memory segment can only be migrated once.
In 2.6.16 through 2.6.17-rc1, shared memory mappings do not have a
migratepage address space op. Therefore, migrate_pages() falls back to
default processing. In this path, it will try to pageout() dirty pages.
Once a shared memory page has been migrated it becomes dirty, so
migrate_pages() will try to page it out. However, because the page count
is 3 [cache + current + pte], pageout() will return PAGE_KEEP because
is_page_cache_freeable() returns false. This will abort all subsequent
migrations.
This patch adds a migratepage address space op to shared memory segments to
avoid taking the default path. We use the "migrate_page()" function
because it knows how to migrate dirty pages. This allows shared memory
segment pages to migrate, subject to other conditions such as # pte's
referencing the page [page_mapcount(page)], when requested.
I think this is safe. If we're migrating a shared memory page, then we
found the page via a page table, so it must be in memory.
Can be verified with memtoy and the shmem-mbind-test script, both
available at: http://free.linux.hp.com/~lts/Tools/
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/shmem.c')
| -rw-r--r-- | mm/shmem.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index 37eaf42ed2c6..4c5e68e4e9ae 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -46,6 +46,8 @@ #include <linux/mempolicy.h> #include <linux/namei.h> #include <linux/ctype.h> +#include <linux/migrate.h> + #include <asm/uaccess.h> #include <asm/div64.h> #include <asm/pgtable.h> @@ -2173,6 +2175,7 @@ static struct address_space_operations shmem_aops = { .prepare_write = shmem_prepare_write, .commit_write = simple_commit_write, #endif + .migratepage = migrate_page, }; static struct file_operations shmem_file_operations = { |