netdev - Re: [PATCH RFC 0/3] tun zerocopy stats

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Date:   Thu, 12 Oct 2017 19:21:12 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH RFC 0/3] tun zerocopy stats



On 2017年10月12日 05:44, Willem de Bruijn wrote:
> On Tue, Oct 10, 2017 at 11:15 PM, Jason Wang <jasowang@...hat.com> wrote:
>>
>> On 2017年10月11日 03:11, Willem de Bruijn wrote:
>>> On Tue, Oct 10, 2017 at 1:39 PM, David Miller <davem@...emloft.net> wrote:
>>>> From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
>>>> Date: Tue, 10 Oct 2017 11:29:33 -0400
>>>>
>>>>> If there is a way to expose these stats through vhost_net directly,
>>>>> instead of through tun, that may be better. But I did not see a
>>>>> suitable interface. Perhaps debugfs.
>>>> Please don't use debugfs, thank you :-)
>>> Okay. I'll take a look at tracing for on-demand measurement.
>>
>> This reminds me a past series that adding tracepoints to vhost/net[1]. It
>> can count zero/datacopy independently and even contains a sample program to
>> show the stats.
> Interesting, thanks!
>
> For occasional evaluation, we can also use a bpf kprobe for the time being:
>
>    bpf_program = """
>    #include <uapi/linux/ptrace.h>
>    #include <bcc/proto.h>
>
>    BPF_ARRAY(count, u64, 2);
>
>    void inc_counter(struct pt_regs *ctx) {
>        bool success;
>        int key;
>        u64 *val;
>
>        success = PT_REGS_PARM2(ctx);
>        key = success ? 0 : 1;
>        val = count.lookup(&key);
>        if (val)
>            lock_xadd(val, 1);
>    }
>    """
>
>    b = bcc.BPF(text=bpf_program)
>    b.attach_kprobe(event="vhost_zerocopy_callback", fn_name="inc_counter")
>
>    time.sleep(5)
>
>    print("vhost_zerocopy_callback: Y:%d N:%d" %
>          (b["count"][ctypes.c_int(0)].value,
>           b["count"][ctypes.c_int(1)].value))

Thanks for the tips, looks flexible.