The patch titled
add migratepage address space op to shmem
has been added to the -mm tree. Its filename is
add-migratepage-address-space-op-to-shmem.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
From: Lee Schermerhorn <Lee.Schermerhorn@xxxxxx>
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@xxxxxx>
Acked-by: Christoph Lameter <clameter@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
mm/shmem.c | 3 +++
1 files changed, 3 insertions(+)
diff -puN mm/shmem.c~add-migratepage-address-space-op-to-shmem mm/shmem.c
--- devel/mm/shmem.c~add-migratepage-address-space-op-to-shmem 2006-04-20 16:45:20.000000000 -0700
+++ devel-akpm/mm/shmem.c 2006-04-20 16:45:20.000000000 -0700
@@ -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>
@@ -2165,6 +2167,7 @@ static struct address_space_operations s
.prepare_write = shmem_prepare_write,
.commit_write = simple_commit_write,
#endif
+ .migratepage = migrate_page,
};
static struct file_operations shmem_file_operations = {
_
Patches currently in -mm which might be from Lee.Schermerhorn@xxxxxx are
add-migratepage-address-space-op-to-shmem.patch
sched_domain-handle-kmalloc-failure-fix.patch
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