[patch 3/3] mm: An enhancement of OVERCOMMIT_GUESS

From: Hideo AOKI
Date: Wed Apr 05 2006 - 19:48:46 EST


There is a copy of __vm_enough_memory() in mm/nommu.c. I believe that
this enhancement is useful for nommu environment too.

---
Hideo Aoki, Hitachi Computer Products (America) Inc.
This patch is an enhancement of OVERCOMMIT_GUESS algorithm in
__vm_enough_memory() in mm/nommu.c.

When the OVERCOMMIT_GUESS algorithm calculates the number of free
pages, the algorithm subtracts the number of reserved pages from
the result nr_free_pages().

Signed-off-by: Hideo Aoki <haoki@xxxxxxxxxx>
---

nommu.c | 18 +++++++++++++++---
1 files changed, 15 insertions(+), 3 deletions(-)

diff -purN linux-2.6.17-rc1-mm1/mm/nommu.c linux-2.6.17-rc1-mm1-idea6/mm/nommu.c
--- linux-2.6.17-rc1-mm1/mm/nommu.c 2006-04-04 10:43:30.000000000 -0400
+++ linux-2.6.17-rc1-mm1-idea6/mm/nommu.c 2006-04-04 15:09:24.000000000 -0400
@@ -1147,14 +1147,26 @@ int __vm_enough_memory(long pages, int c
* only call if we're about to fail.
*/
n = nr_free_pages();
+
+ /*
+ * Leave reserved pages. The pages are not for anonymous pages.
+ */
+ if (n <= totalreserve_pages)
+ goto error;
+ else
+ n -= totalreserve_pages;
+
+ /*
+ * Leave the last 3% for root
+ */
if (!cap_sys_admin)
n -= n / 32;
free += n;

if (free > pages)
return 0;
- vm_unacct_memory(pages);
- return -ENOMEM;
+
+ goto error;
}

allowed = totalram_pages * sysctl_overcommit_ratio / 100;
@@ -1175,7 +1187,7 @@ int __vm_enough_memory(long pages, int c
*/
if (atomic_read(&vm_committed_space) < (long)allowed)
return 0;
-
+error:
vm_unacct_memory(pages);

return -ENOMEM;