The patch titled mm: make do_move_pages() complexity linear has been removed from the -mm tree. Its filename was mm-make-do_move_pages-complexity-linear-fix.patch This patch was dropped because it was nacked The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: mm: make do_move_pages() complexity linear From: Brice Goglin <Brice.Goglin@xxxxxxxx> > +/* > + * Allocate a page on the node given as a page_to_node in private. > + * Increase private to point to the next page_to_node so that the > + * next iteration does not have to traverse the whole pm array. > + */ > static struct page *new_page_node(struct page *p, unsigned long private, > int **result) > { > - struct page_to_node *pm = (struct page_to_node *)private; > + struct page_to_node **pmptr = (struct page_to_node **)private; > + struct page_to_node *pm = *pmptr; > > while (pm->node != MAX_NUMNODES && pm->page != p) > pm++; > > + /* prepare for the next iteration */ > + *pmptr = pm + 1; > + > Actually, this "pm+1" breaks the case where migrate_pages() calls unmap_and_move() multiple times on the same page. In this case, we need the while loop to look at pm instead of pm+1 first. So we can't cache pm+1 in private, but caching pm is ok. There will be 1 while loop instead of 0 in the regular case. Updated patch (with more comments) coming soon. Signed-off-by: Brice Goglin <Brice.Goglin@xxxxxxxx> Signed-off-by: Nathalie Furmento <Nathalie.Furmento@xxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx> Cc: Mel Gorman <mel@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/migrate.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff -puN mm/migrate.c~mm-make-do_move_pages-complexity-linear-fix mm/migrate.c --- a/mm/migrate.c~mm-make-do_move_pages-complexity-linear-fix +++ a/mm/migrate.c @@ -839,8 +839,14 @@ struct page_to_node { /* * Allocate a page on the node given as a page_to_node in private. - * Increase private to point to the next page_to_node so that the - * next iteration does not have to traverse the whole pm array. + * + * Cache the _last used_ pm in private so that the next call may find the + * target pm in very few while loops (usually 1) instead of scanning the + * whole pm array. + * We cannot cache the _next_ pm in private (to get 0 while loop in the + * regular case) because it would break the case where new_page_node() + * is called multiple times on the same page (when migrate_pages() tries + * unmap_and_move() multiple times). */ static struct page *new_page_node(struct page *p, unsigned long private, int **result) @@ -851,8 +857,8 @@ static struct page *new_page_node(struct while (pm->node != MAX_NUMNODES && pm->page != p) pm++; - /* prepare for the next iteration */ - *pmptr = pm + 1; + /* save the current pm to reduce the while loop in the next call */ + *pmptr = pm; if (pm->node == MAX_NUMNODES) return NULL; _ Patches currently in -mm which might be from Brice.Goglin@xxxxxxxx are mm-make-do_move_pages-complexity-linear-fix.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html