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. IOW I'm wondering if there's any workload where this patch makes a difference.
