Re: Kernel 4.6.7-rt13: Intel Ethernet driver igb causes huge latencies in cyclictest
From: Richard Cochran <richardcochran@gmail.com>
Date: 2016-10-14 22:07:01
Also in:
intel-wired-lan, linux-rt-users
On Fri, Oct 14, 2016 at 08:58:22AM +0000, Koehrer Mathias (ETAS/ESW5) wrote:
quoted hunk ↗ jump to hunk
@@ -753,7 +756,9 @@ u32 igb_rd32(struct e1000_hw *hw, u32 re if (E1000_REMOVED(hw_addr)) return ~value; + trace_igb(801); value = readl(&hw_addr[reg]); + trace_igb(802);
Nothing prevents this code from being preempted between the two trace points, and so you can't be sure whether the time delta in the trace is caused by the PCIe read stalling or not. Thanks, Richard