diff options
author | Christoph Lameter <clameter@engr.sgi.com> | 2006-02-10 01:51:15 -0800 |
---|---|---|
committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-02-10 08:13:13 -0800 |
commit | 418aade459f03318defd18ef0b11981a63bd81b0 (patch) | |
tree | b13a46e3d7050fa92e390b3374910882ae867254 | |
parent | 8977d929e49021d9a6e031310aab01fa72f849c2 (diff) |
[PATCH] Updates for page migration
This adds some additional comments in order to help others figure out how
exactly the code works. And fix a variable name.
Also swap_page does need to ignore all reference bits when unmapping a
page. Otherwise we may have to repeatedly unmap a frequently touched page.
So change the try_to_unmap parameter to 1.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r-- | mm/vmscan.c | 25 |
1 files changed, 20 insertions, 5 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index 5a610804cd06..5db32fdfaf39 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -632,7 +632,7 @@ static int swap_page(struct page *page) struct address_space *mapping = page_mapping(page); if (page_mapped(page) && mapping) - if (try_to_unmap(page, 0) != SWAP_SUCCESS) + if (try_to_unmap(page, 1) != SWAP_SUCCESS) goto unlock_retry; if (PageDirty(page)) { @@ -839,7 +839,7 @@ EXPORT_SYMBOL(migrate_page); * pages are swapped out. * * The function returns after 10 attempts or if no pages - * are movable anymore because t has become empty + * are movable anymore because to has become empty * or no retryable pages exist anymore. * * Return: Number of pages not migrated when "to" ran empty. @@ -928,12 +928,21 @@ redo: goto unlock_both; if (mapping->a_ops->migratepage) { + /* + * Most pages have a mapping and most filesystems + * should provide a migration function. Anonymous + * pages are part of swap space which also has its + * own migration function. This is the most common + * path for page migration. + */ rc = mapping->a_ops->migratepage(newpage, page); goto unlock_both; } /* - * Trigger writeout if page is dirty + * Default handling if a filesystem does not provide + * a migration function. We can only migrate clean + * pages so try to write out any dirty pages first. */ if (PageDirty(page)) { switch (pageout(page, mapping)) { @@ -949,9 +958,10 @@ redo: ; /* try to migrate the page below */ } } + /* - * If we have no buffer or can release the buffer - * then do a simple migration. + * Buffers are managed in a filesystem specific way. + * We must have no buffers or drop them. */ if (!page_has_buffers(page) || try_to_release_page(page, GFP_KERNEL)) { @@ -966,6 +976,11 @@ redo: * swap them out. */ if (pass > 4) { + /* + * Persistently unable to drop buffers..... As a + * measure of last resort we fall back to + * swap_page(). + */ unlock_page(newpage); newpage = NULL; rc = swap_page(page); |