On Fri, 17 Feb 2012 16:00:14 -0800 (PST)
Hugh Dickins <hughd@xxxxxxxxxx> wrote:
> Not a functional change, just a minor internal cleanup: move the
> buffer_heads_over_limit processing up from move_active_pages_to_lru()
> (where it has to drop lock and reloop) to its caller shrink_active_list().
>
> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
> ---
> mm/vmscan.c | 19 +++++++------------
> 1 file changed, 7 insertions(+), 12 deletions(-)
>
> --- mmotm.orig/mm/vmscan.c 2012-02-07 16:59:13.000000000 -0800
> +++ mmotm/mm/vmscan.c 2012-02-07 17:07:23.800524771 -0800
> @@ -1641,18 +1641,6 @@ static void move_active_pages_to_lru(str
> unsigned long pgmoved = 0;
> struct page *page;
>
> - if (buffer_heads_over_limit) {
> - spin_unlock_irq(&zone->lru_lock);
> - list_for_each_entry(page, list, lru) {
> - if (page_has_private(page) && trylock_page(page)) {
> - if (page_has_private(page))
> - try_to_release_page(page, 0);
> - unlock_page(page);
> - }
> - }
> - spin_lock_irq(&zone->lru_lock);
> - }
> -
> while (!list_empty(list)) {
> struct lruvec *lruvec;
>
> @@ -1734,6 +1722,13 @@ static void shrink_active_list(unsigned
> continue;
> }
>
> + if (buffer_heads_over_limit &&
> + page_has_private(page) && trylock_page(page)) {
> + if (page_has_private(page))
> + try_to_release_page(page, 0);
> + unlock_page(page);
> + }
> +
> if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) {
> nr_rotated += hpage_nr_pages(page);
> /*
yup.
I don't think there's a lot of point in trying to micro-optimise the
buffer_heads_over_limit==true case, either. But I suppose that
pointlessly locking 1000000 anon pages is indeed pointless. Hopefully
there _is_ a point in micro-optimising the actual test for
buffer_heads_over_limit==true. So...
--- a/mm/vmscan.c~mm-vmscan-forcibly-scan-highmem-if-there-are-too-many-buffer_heads-pinning-highmem-fix-fix
+++ a/mm/vmscan.c
@@ -1723,11 +1723,12 @@ static void shrink_active_list(unsigned
continue;
}
- if (buffer_heads_over_limit &&
- page_has_private(page) && trylock_page(page)) {
- if (page_has_private(page))
- try_to_release_page(page, 0);
- unlock_page(page);
+ if (unlikely(buffer_heads_over_limit)) {
+ if (page_has_private(page) && trylock_page(page)) {
+ if (page_has_private(page))
+ try_to_release_page(page, 0);
+ unlock_page(page);
+ }
}
if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) {
_
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