nouveau. swiotlb: coherent allocation failed for device 0000:01:00.0 size=2097152

[Mike Galbraith]

On Sun, 2017-12-31 at 13:27 -0500, Ilia Mirkin wrote:
> On Tue, Dec 19, 2017 at 8:45 AM, Christian König
> <ckoenig.leichtzumerken at gmail.com> wrote:
> > Am 19.12.2017 um 11:39 schrieb Michel Dänzer:
> >>
> >> On 2017-12-19 11:37 AM, Michel Dänzer wrote:
> >>>
> >>> On 2017-12-18 08:01 PM, Tobias Klausmann wrote:
> >>>>
> >>>> On 12/18/17 7:06 PM, Mike Galbraith wrote:
> >>>>>
> >>>>> Greetings,
> >>>>>
> >>>>> Kernel bound workloads seem to trigger the below for whatever reason.
> >>>>>    I only see this when beating up NFS.  There was a kworker wakeup
> >>>>> latency issue, but with a bandaid applied to fix that up, I can still
> >>>>> trigger this.
> >>>>
> >>>>
> >>>> Hi,
> >>>>
> >>>> i have seen this one as well with my system, but i could not find an
> >>>> easy way to trigger it for bisecting purpose. If you can trigger it
> >>>> conveniently, a bisect would be nice!
> >>>
> >>> I'm seeing this (with the amdgpu and radeon drivers) when restic takes a
> >>> backup, creating memory pressure. I happen to have just finished
> >>> bisecting, the result is:
> >>>
> >>> 648bc3574716400acc06f99915815f80d9563783 is the first bad commit
> >>> commit 648bc3574716400acc06f99915815f80d9563783
> >>> Author: Christian König <christian.koenig at amd.com>
> >>> Date:   Thu Jul 6 09:59:43 2017 +0200
> >>>
> >>>      drm/ttm: add transparent huge page support for DMA allocations v2
> >>>
> >>>      Try to allocate huge pages when it makes sense.
> >>>
> >>>      v2: fix comment and use ifdef
> >>>
> >>>
> >> BTW, I haven't noticed any bad effects other than the dmesg splats, so
> >> maybe it's just noise about transient failures for which there is a
> >> proper fallback in place.
> >
> >
> > Yeah, I think that is exactly what happens here.
> >
> > We try to allocate a huge page, but fail and so fall back to using multiple
> > 4k pages instead.
> >
> > Going to send out a patch to suppress the warning.
> 
> Hi Christian,
> 
> Did you ever send out such a patch? I didn't see one on the list, but
> perhaps I missed it. One definitely hasn't made it upstream yet. (I
> just hit the issue myself with Linus's tree from last night.)

Actually, that wants a bit more methinks, because while the stack dump
goes away, you still get spammed, it just comes in smaller chunks.

	-Mike