Re: Kernel memory leak with x11/nvidia-driver

On 02/ 4/16 08:05 PM, Mark Johnston wrote:
> 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;
>   

Your patch fixes the leak completely.  Nice work, Mark!

I didn't notice the leak until I unknowingly left the screensaver 
cycling all overnight.  In my normal workflow, I open the windows I need 
and pretty much leave them there.  This doesn't seem to trigger the 
leak, at least not at a noticeable rate.

Thanks for your help!

Eric