On Mon, Aug 07, 2017 at 09:52:24AM -0600, Alex Williamson wrote: > I wonder if it has something to do > with the link speed/width advertised on the switch port. I don't think > the endpoint can actually downshift the physical link, so lspci on the > host should probably still show the full bandwidth capability, but > maybe the driver is somehow doing rate limiting. PCIe gets a little > more complicated as we go to newer versions, so it's not quite as > simple as exposing a different bit configuration to advertise 8GT/s, > x16. Last I tried to do link matching it was deemed too complicated > for something I couldn't prove at the time had measurable value. This > might be a good way to prove that value if it makes a difference here. > I can't think why else you'd see such a performance difference, but > testing to see if the KVM exit rate is significantly different could > still be an interesting verification.
It might be easiest to just dust off that patch and see whether it helps. -- MST
