[dpdk-dev] net/i40e: latency issue due fix interrupt throttling setting in PF

[Hanoch Haim (hhaim)]

Re-sending

Hanoh

From: Hanoch Haim (hhaim)
Sent: Monday, November 20, 2017 5:19 PM
To: dev at dpdk.org
Cc: Wu, Jingjing (jingjing.wu at intel.com); Hanoch Haim (hhaim)
Subject: [dpdk-dev] net/i40e: latency issue due fix interrupt throttling setting in PF

Hi All,
While integrating dpdk17.11 into TRex latest code a new latency issue is observed  (i40e is very sensitive because it has very good resolution due to Qos configuration).
git bitsec found the following commit.
With this commit we observe high spikes of Rx latency (~40usec) vs (~8usec).
Any idea why?
I can send how to reproduce this, it is very simple.

cfd662d22e7bddb4ba41dbd1384f8497f38c2b4e is the first bad commit
commit cfd662d22e7bddb4ba41dbd1384f8497f38c2b4e
Author: Jingjing Wu <jingjing.wu at intel.com<mailto:jingjing.wu at intel.com>>
Date:   Thu Aug 24 09:57:51 2017 +0800

    net/i40e: fix interrupt throttling setting in PF

    As no matter the PF host driver is DPDK or other kernel drivers,
    they are sharing the same virtchnnl interfaces to communicate to VFs.
    To follow the generic interface, DPDK PF need to set Interrupt
    Throttling (ITR) index according to the rxitr_idx from virtchnnl
    instead of ITR_NONE.

    Fixes: 6d59e4ea74a6 ("net/i40e: change version number to support Linux VF")
    Cc: stable at dpdk.org<mailto:stable at dpdk.org>

    Signed-off-by: Jingjing Wu <jingjing.wu at intel.com<mailto:jingjing.wu at intel.com>>



Thanks,
Hanoh