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

From: Christian KÃnig
Date: Tue Dec 19 2017 - 08:45:14 EST

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:

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.


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,