From: Jes Sorensen <jes@trained-monkey.org>
nr_free_pages() is expensive, especially on large SMP machines. The patch
changes the memory overcommit code so that it only calls nr_free_pages() is
we're about to fail the allocation attempt.
---
25-akpm/security/commoncap.c | 15 ++++++++++++++-
1 files changed, 14 insertions(+), 1 deletion(-)
diff -puN security/commoncap.c~nr_free_pages-is-expensive security/commoncap.c
--- 25/security/commoncap.c~nr_free_pages-is-expensive Wed Jan 28 13:16:42 2004
+++ 25-akpm/security/commoncap.c Wed Jan 28 13:18:16 2004
@@ -321,8 +321,9 @@ int cap_vm_enough_memory(long pages)
return 0;
if (sysctl_overcommit_memory == 0) {
+ unsigned long n;
+
free = get_page_cache_size();
- free += nr_free_pages();
free += nr_swap_pages;
/*
@@ -341,6 +342,18 @@ int cap_vm_enough_memory(long pages)
if (free > pages)
return 0;
+
+ /*
+ * nr_free_pages() is very expensive on large systems,
+ * only call if we're about to fail.
+ */
+ n = nr_free_pages();
+ if (!capable(CAP_SYS_ADMIN))
+ n -= n / 32;
+ free += n;
+
+ if (free > pages)
+ return 0;
vm_unacct_memory(pages);
return -ENOMEM;
}
_