Hi experts, I'm working with different NIC devices, and I've seen that some of them don't have a "good" PTP performance (later I'll describe what I define as "good"). I decided to run a short test, and write a comparison table. I believe that maybe some of you are familiar with the behaviour I've encountered.
The NICs unders test are (all Intel): I210, 82574L, I218-V, I219-V. My setup is as described below: [NIC under test / MASTER] <---- [2 meter cable] ----> [KSZ9477 / SLAVE] The Slave is always KSZ9477. Only the Master is replaced between each test. There is only a cable between Master and Slave. No other devices or switches. Both master and slave support HW timestamping. NIC Driver Version FW-Version Test Results Intel I210 igb 5.4.0-k 3.25, 0x80000678 GOOD Intel 82574L e1000e 3.2.6-k 1.8-0 GOOD Intel I218-V e1000e 3.2.6-k 0.2-4 BAD Intel I218-V e1000e 3.8.7-NAPI 0.2-4 BAD Intel I219-V e1000e 3.2.6-k 0.4-4 BAD Test results description: GOOD: Delay is always around 20 nsec (10 nsec jitter), even under heavy traffic. Offset is always < 200 nsec, even under heavy traffic. BAD: Unstable delay. With no traffic, the delay is around 7500-8000 nsec. Under heavy traffic it gets smaller - reaching a delay of 800 nsec and stabilizes on 800 nsec. When traffic goes off, delay reaches back to 7500-8000 nsec. Offset can jitter up to 5000 nsec, but it stabilizes when the delay is stabilized. The interesting thing I saw in the I218/I219 is that after a while of traffic (1 or 2 minutes), the delay is stabilized on 800 nsec, and when I turn off the traffic, the delay is still left stabilized on 800 nsec for a ~15 seconds, and only then starts go back to its original value of 7500-8000 nesc (and same behaviour vice versa). I must say it looks more like a feature than a bug (that maybe I just need to disable). I thought maybe: EEE, Low Power Mode or Flow Control (I tried disabling them with ethtool, but results didn't change - maybe using ethtool is not the right way to do that...) Does anyone is familiar with such a behaviour with Intel I218/I219 ? Thanks, Joseph
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