[PATCH, RFC] mm: Implement RLIMIT_RSS

["Jörn Engel" <joern@logfs.org>]

I've seen a couple of instances where people try to impose a vsize
limit simply because there is no rss limit in Linux.  The vsize limit
is a horrible approximation and even this patch seems to be an
improvement.

Would there be strong opposition to actually supporting RLIMIT_RSS?

Jörn

--
It's not whether you win or lose, it's how you place the blame.
-- unknown


Not quite perfect, but close enough for many purposes.  This checks rss
limit inside may_expand_vm() and will fail if we are already over the
limit.

Signed-off-by: Joern Engel <joern@logfs.org>
---
 mm/mmap.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index ab652fa..ea90c73 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2446,12 +2446,19 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
 int may_expand_vm(struct mm_struct *mm, unsigned long npages)
 {
 	unsigned long cur = mm->total_vm;	/* pages */
-	unsigned long lim;
+	unsigned long lim, rlim;
 
 	lim = rlimit(RLIMIT_AS) >> PAGE_SHIFT;
+	rlim = rlimit(RLIMIT_RSS) >> PAGE_SHIFT;
 
 	if (cur + npages > lim)
 		return 0;
+	if (cur + npages > rlim) {
+		/* Yes, the rss limit is somewhat imprecise. */
+		if (get_mm_rss(mm) > rlim) {
+			return 0;
+		}
+	}
 	return 1;
 }
 
-- 
1.7.10.4