diff options
| author | Lee Schermerhorn <Lee.Schermerhorn@hp.com> | 2006-04-22 02:35:48 -0700 |
|---|---|---|
| committer | Chris Wright <chrisw@sous-sol.org> | 2006-05-20 15:00:33 -0700 |
| commit | 75178298c6c807a7274ab48ef9c4d6be7d0114d8 (patch) | |
| tree | edaed2ed2e3a69808b84f5d1118c205674247621 /mm/shmem.c | |
| parent | 602e0343a69b4300de4b889d644f95983dfdc9cd (diff) | |
[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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Diffstat (limited to 'mm/shmem.c')
| -rw-r--r-- | mm/shmem.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index 7c455fbaff7..f0eb2f265eb 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2172,6 +2172,7 @@ 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 = { |