Re: [dpdk-users] Does vmxnet3 PMD supports LSC=1 ?

[Yong Wang <yongwang@vmware.com>]

Vmxnet3 driver supports lsc and your observation is a known behavior with vmxnet3 running with INTx/MSI interrupt mode.  Enabling or disabling lsc intr in this mode will enable/disable RX interrupts as well.  This is a device behavior and there is no known way to mask just lsc or rx interrupts as the mask is per vector.  To work around this, either disable interrupt or move to msi-x. Currently the upstream dpdk vmxnet3 driver does not support msix.  We have plans to upstream vmxnet3 msix support in the future.

Yong

-----Original Message-----
From: Thomas Monjalon <thomas@monjalon.net>
Date: Thursday, January 14, 2021 at 10:50 AM
To: madhukar mythri <madhukar.mythri@gmail.com>
Cc: "users@dpdk.org" <users@dpdk.org>, Yong Wang <yongwang@vmware.com>
Subject: Re: [dpdk-users] Does vmxnet3 PMD supports LSC=1 ?

    +Cc Yong Wang, maintainer of this PMD.

    14/01/2021 18:30, madhukar mythri:
    > Hi,
    > 
    > Does vmxnet3 PMD support LSC=1(i.e with interrupt mode) for link changes ?
    > 
    > When i enable LSC=1 the functionality works fine, but, when pumping traffic
    > i'm seeing increasing in CPU load on some cores which is running
    > "eal-intr-thread" epoll_wait() function for more CPU-time.
    > 
    > Actually, interrupt should come only when Link changes, but, we are seeing
    > interrupt for each incoming Rx-packet and also a lot of spurious interrupts.
    > =============
    > ~ # cat /proc/interrupts |grep igb
    >  58:    1254293          0          0          0   PCI-MSI 1572864-edge
    >  igb_uio
    >  59:    1278105          0          0          0   PCI-MSI 5767168-edge
    >  igb_uio
    > ~ # cat /proc/irq/58/spurious
    > count 98035
    > unhandled 0
    > last_unhandled 0 ms
    > ~ #
    > ==============
    > 
    > Does anyone tried LSC=1 in vmxnet3 PMD based apps and faced similar issues
    > ? If so, please let me know.
    > 
    > Tried with DPDK-18.11, DPDK-19.11 and DPDK-20.05.
    > 
    > Thanks,
    > Madhukar.