On Mon, Jul 15, 2019 at 04:10:36PM -0700, Andy Lutomirski wrote: > On Mon, Jul 15, 2019 at 3:53 PM Andi Kleen <a...@linux.intel.com> wrote: > > > > > I haven't tested on a real kernel with i915. Does i915 really hit > > > this code path? Does it happen more than once or twice at boot? > > > > Yes some workloads allocate/free a lot of write combined memory > > for graphics objects. > > > > But where does that memory come from? If it's from device memory > (i.e. memory that's not in the kernel direct map), then, unless I > missed something, we're never changing the cache mode per se -- we're > just ioremap_wc-ing it, which doesn't require a flush.
Integraded graphics doesn't have device memory. There's an reserved memory area, but a lot of the buffers the GPU works with come from main memory. -Andi
