[PATCH] Zone reclaim: resurrect may_swap

Zone reclaim has a huge impact on NUMA performance (f.e.  our maximum
throughput with XFS is raised from 4GB to 6GB/sec / page cache contamination
of numa nodes destroys locality if one just does a large copy operation which
results in performance dropping for good until reboot).

This patch:

Resurrect may_swap in struct scan_control

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 827bf674577a..e5117b6897a9 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -71,6 +71,9 @@ struct scan_control {
 
         int may_writepage;
 
+        /* Can pages be swapped as part of reclaim? */
+        int may_swap;
+
         /* This context's SWAP_CLUSTER_MAX. If freeing memory for
          * suspend, we effectively ignore SWAP_CLUSTER_MAX.
          * In this context, it doesn't matter that we scan the
@@ -458,6 +461,8 @@ static int shrink_list(struct list_head *page_list, struct scan_control *sc)
                  * Try to allocate it some swap space here.
                  */
                 if (PageAnon(page) && !PageSwapCache(page)) {
+                        if (!sc->may_swap)
+                                goto keep_locked;
                         if (!add_to_swap(page, GFP_ATOMIC))
                                 goto activate_locked;
                 }
@@ -1166,6 +1171,7 @@ int try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
 
         sc.gfp_mask = gfp_mask;
         sc.may_writepage = 0;
+        sc.may_swap = 1;
 
         inc_page_state(allocstall);
 
@@ -1268,6 +1274,7 @@ loop_again:
         total_reclaimed = 0;
         sc.gfp_mask = GFP_KERNEL;
         sc.may_writepage = 0;
+        sc.may_swap = 1;
         sc.nr_mapped = read_page_state(nr_mapped);
 
         inc_page_state(pageoutrun);