[Xen-devel] [PATCH] linux/balloon: prefer using pages from balloon in alloc_empty_pages_and_pagevec()

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

This is both faster and less demanding on kernel resources.

Likely also something that could be done in the pv-ops tree (though it
would need some adjustment to deal with the balloon_order!=0 case).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- head-2009-12-07.orig/drivers/xen/balloon/balloon.c  2009-12-15 
09:37:50.000000000 +0100
+++ head-2009-12-07/drivers/xen/balloon/balloon.c       2009-12-15 
09:47:04.000000000 +0100
@@ -607,6 +607,17 @@ struct page **alloc_empty_pages_and_page
                return NULL;
 
        for (i = 0; i < nr_pages; i++) {
+               balloon_lock(flags);
+               page = balloon_first_page();
+               if (page && !PageHighMem(page)) {
+                       UNLIST_PAGE(page);
+                       bs.balloon_low--;
+                       balloon_unlock(flags);
+                       pagevec[i] = page;
+                       continue;
+               }
+               balloon_unlock(flags);
+
                page = pagevec[i] = alloc_page(GFP_KERNEL|__GFP_COLD);
                if (page == NULL)
                        goto err;




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