netdev - Re: [PATCH v2 net-next 4/4] udp: add batching to udp_rmem

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Message-ID: <CANn89i+10fwMQ+oqs2AgVfE9CHnpZqecN_NxVqobyzD1riyMfg@mail.gmail.com>
Date:   Thu, 8 Dec 2016 10:38:51 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH v2 net-next 4/4] udp: add batching to udp_rmem_release()

On Thu, Dec 8, 2016 at 10:36 AM, Eric Dumazet <edumazet@...gle.com> wrote:
> On Thu, Dec 8, 2016 at 10:24 AM, Paolo Abeni <pabeni@...hat.com> wrote:
>
>> Nice one! This sounds like a relevant improvement!
>>
>> I'm wondering if it may cause regressions with small value of
>> sk_rcvbuf ?!? e.g. with:
>>
>> netperf -t UDP_STREAM  -H 127.0.0.1 -- -s 1280 -S 1280 -m 1024 -M 1024
>>
>
> Possibly, then simply we can refine the test to :
>
> size = up->forward_deficit;
> if (size < (sk->sk_rcvbuf >> 2)  && !skb_queue_empty(sk->sk_receive_buf))
>      return;

BTW, I tried :

lpaa6:~# ./netperf -t UDP_STREAM  -H 127.0.0.1 -- -s 1280 -S 1280 -m
1024 -M 1024
MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to
127.0.0.1 () port 0 AF_INET
Socket  Message  Elapsed      Messages
Size    Size     Time         Okay Errors   Throughput
bytes   bytes    secs            #      #   10^6bits/sec

  4608    1024   10.00     4499400      0    3685.88
  2560           10.00     4498670           3685.28

So it looks like it is working.

However I have no doubt there might be a corner case for tiny
SO_RCVBUF values or for some message sizes.