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

[Christian KÃnig]

Am 19.12.2017 um 11:39 schrieb Michel DÃnzer:
> On 2017-12-19 11:37 AM, Michel DÃnzer 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.
> > > >  ÂÂI only see this when beating up NFS. ÂThere 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 KÃnig <christian.koenig@xxxxxxx>
> > 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.

Thanks for bisecting this,
Christian.