Re: Kernel memory leak with x11/nvidia-driver

On Thu, Feb 04, 2016 at 05:37:24PM -0600, Eric van Gyzen wrote:
> On 02/ 3/16 10:54 AM, Eric van Gyzen wrote:
> > I just set up a new desktop running head with x11/nvidia-driver.  I've
> > discovered a memory leak where pages disappear from the queues, never to
> > return.  Specifically, the total of
> >      v_active_count
> >      v_inactive_count
> >      v_wire_count
> >      v_cache_count
> >      v_free_count
> > drops, eventually becoming /much/ less than v_page_count.  After leaving
> > xscreensaver running overnight, cycling the saver every 10 minutes, the
> > system was unusable, because it only had a few MB of memory.  (It has 8
> > GB physical.)
> 
> In case anyone is curious, /usr/local/bin/xscreensaver-hacks/glmatrix 
> triggers a fairly fast leak--around 600 pages per second.

I'm able to repro this on my workstation. With DTrace I can see that
glmatrix is allocating pages for an SG object at roughly the rate
they're being leaked. I took a look at r292373 (based on the history of
sg_pager.c) and noticed a vm_page_free() call was lost when
sg_pager_getpages() was simplified.

The patch below seems to do the trick for me. Could you give it a try
and confirm that it fixes the problem? I run current+nvidia-driver on
multiple workstations but hadn't observed a leak until now, so maybe
there's something additional going on in your case. Then again, I just
use i3lock. :)

diff --git a/sys/vm/sg_pager.c b/sys/vm/sg_pager.c
index 84bfa49..2cccb7ea 100644
--- a/sys/vm/sg_pager.c
+++ b/sys/vm/sg_pager.c
_at__at_ -189,6 +189,9 _at__at_ sg_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
 	VM_OBJECT_WLOCK(object);
 	TAILQ_INSERT_TAIL(&object->un_pager.sgp.sgp_pglist, page, plinks.q);
 	vm_page_replace_checked(page, object, offset, m[0]);
+	vm_page_lock(m[0]);
+	vm_page_free(m[0]);
+	vm_page_unlock(m[0]);
 	m[0] = page;
 	page->valid = VM_PAGE_BITS_ALL;