netdev - Re: [PATCH net 2/4] net/udpgso_bench_tx: options to exercise TX CMSG

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Date:   Thu, 23 May 2019 17:52:53 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Fred Klassen <fklassen@...neta.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Shuah Khan <shuah@...nel.org>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-kselftest@...r.kernel.org,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net 2/4] net/udpgso_bench_tx: options to exercise TX CMSG

On Thu, May 23, 2019 at 5:11 PM Fred Klassen <fklassen@...neta.com> wrote:
>
> This enhancement adds options that facilitate load testing with
> additional TX CMSG options, and to optionally print results of
> various send CMSG operations.
>
> These options are especially useful in isolating situations
> where error-queue messages are lost when combined with other
> CMSG operations (e.g. SO_ZEROCOPY).
>
> New options:
>
>     -T - add TX CMSG that requests TX software timestamps
>     -H - similar to -T except request TX hardware timestamps
>     -q - add IP_TOS/IPV6_TCLASS TX CMSG

To ensure that we do not regress, when adding options, please consider
(just a general suggestion, not a strong request for this patch set)
updating the kselftest to run a variant of the test with the new code
coverage. In this case, make the code pass/fail instead of only user
interpretable and add variants to udpgso.sh.

>     -P - call poll() before reading error queue
>     -v - print detailed results
>
> Fixes: 3a687bef148d ("selftests: udp gso benchmark")
> Signed-off-by: Fred Klassen <fklassen@...neta.com>

> +static void flush_errqueue_recv(int fd)
>  {
>         struct msghdr msg = {0};        /* flush */
> +       struct cmsghdr *cmsg;
> +       struct iovec entry;
> +       char control[1024];

can use more precise CMSG_SPACE based on worst case expectations, like
in udp_sendmmsg

> +       char buf[1500];

no need for payload

> +static void flush_errqueue(int fd)
> +{
> +       if (cfg_poll) {
> +               struct pollfd fds = { 0 };
> +               int ret;
> +
> +               fds.fd = fd;
> +               fds.events = POLLERR;

no need to pass POLLERR, it is always returned in revents.