[Bug 218525] Thunderbolt eGPU bad performance

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=218525

--- Comment #9 from Mika Westerberg (mika.westerberg@linux.intel.com) ---
Okay I see a couple of things from HW side that may affect (or may not). First
is that the real PCIe link to the 06:00 eGPU device is running on limited
bandwidth:

                LnkSta: Speed 5GT/s (downgraded), Width x4 (downgraded)
                        TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt-


I don't know why this is but it could be that the graphics driver tunes this
because it finds the virtual links only supporting gen 1 speeds. However, this
is not true, the virtual PCIe links over Thunderbolt can get up to 90% of the
40G link if there is no other tunneling (such as DisplayPort).

The second thing is that there is ASPM L1 enabled on this same real PCIe link:

                LnkCtl: ASPM L1 Enabled; RCB 64 bytes, Disabled- CommClk+
                        ExtSynch- ClockPM+ AutWidDis- BWInt- AutBWInt-

I suggest trying to disable it. Passing something like
"pcie_aspm.policy=performance" should make the above to turn into ASPM disabled
or so.

Also I suggest experimenting to disable IOMMU (pass intel_iommu=off in the
kernel command line).

-- 
You may reply to this email to add a comment.

You are receiving this mail because:
You are watching the assignee of the bug.