RE: Kernel 4.6.7-rt13: Intel Ethernet driver igb causes huge latencies in cyclictest

Hi all, > > >> > > >> Can you continue your bisection using 'git bisect'? You've already > > >> narrowed it down between 4.0 and 4.1, so you're well on your way. > > >> > > > > > > OK - done. > > > And finally I was successful! > > > The following git commit is the one that is causing the

RE: Kernel 4.6.7-rt13: Intel Ethernet driver igb causes huge latencies in cyclictest

Hi Julia! > > > Have you tested on a vanilla (non-RT) kernel? I doubt there is > > > anything RT specific about what you are seeing, but it might be nice > > > to get confirmation. Also, bisection would probably be easier if you > > > confirm on a > vanilla kernel. > > > > > > I find it

RE: Kernel 4.6.7-rt13: Intel Ethernet driver igb causes huge latencies in cyclictest

Hi Julia, > Have you tested on a vanilla (non-RT) kernel? I doubt there is anything RT > specific > about what you are seeing, but it might be nice to get confirmation. Also, > bisection > would probably be easier if you confirm on a vanilla kernel. > > I find it unlikely that it's a kernel

RE: Kernel 4.6.7-rt13: Intel Ethernet driver igb causes huge latencies in cyclictest

Hi all! > > Hi Julia, > > thanks for the detailed analysis! > > > > [...] > > Okay, we finally received our wakeup event. We were expecting to be > > woken up at 10024735653388ns, but were actually woken up at > 10024735682387ns. > > > > 10024735682387 - 10024735653388 = 28999ns > > > > Our

Re: Kernel 4.6.7-rt13: Intel Ethernet driver igb causes huge latencies in cyclictest

Hi Julia, thanks for the detailed analysis! > > [...] > Okay, we finally received our wakeup event. We were expecting to be woken up > at > 10024735653388ns, but were actually woken up at 10024735682387ns. > > 10024735682387 - 10024735653388 = 28999ns > > Our timer fired ~29us late! But

Re: Kernel 4.6.7-rt13: Intel Ethernet driver igb causes huge latencies in cyclictest

Hi Mitch, > > > > > > Although, to be clear, it isn't the fact that there exists 8 > > > threads, it's > > that the device is > > > firing all 8 interrupts at the same time. The time spent in hardirq > > context just waking > > > up all 8 of those threads (and the cyclictest wakeup) is enough to

Re: Kernel 4.6.7-rt13: Intel Ethernet driver igb causes huge latencies in cyclictest

Hi all, > > Although, to be clear, it isn't the fact that there exists 8 threads, it's > that the device is > firing all 8 interrupts at the same time. The time spent in hardirq context > just waking > up all 8 of those threads (and the cyclictest wakeup) is enough to cause your > regression.

Intel Ethernet driver igb causes huge latencies with cyclictest (rt-tests)

Hi all, I noticed that with fairly new versions of the Linux kernel, the igb driver causes huge latencies with the cyclictest in a RT_PREEMPT environment. The root cause seems to be the number of interrupts that are used for the igb NIC devices as multiple of these irqs may occur at the same time