netdev - Re: Socket buffer sizes with autotuning

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Date:	Mon, 28 Apr 2008 12:21:53 -0700
From:	"John Heffner" <johnwheffner@...il.com>
To:	"Jerry Chu" <hkchu@...gle.com>
Cc:	"David Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	rick.jones2@...com
Subject: Re: Socket buffer sizes with autotuning

On Mon, Apr 28, 2008 at 11:30 AM, Jerry Chu <hkchu@...gle.com> wrote:
>  Correct, but its counterpart doesn't exist in tcp_is_cwnd_limited(). So
>  cwnd will continue to grow when left < cwnd/sysctl_tcp_tso_win_divisor,
>  which can be very large when cwnd is large.
>
>  If I change tcp_tso_win_divisor to 0, cwnd max out at 695 rather than 1037,
>  exactly off by 1/3. I tried to add the same check to tcp_is_cwnd_limited():
>
>  diff -c /tmp/tcp.h.old tcp.h
>  *** /tmp/tcp.h.old      Mon Apr 28 11:00:44 2008
>  --- tcp.h       Mon Apr 28 10:54:10 2008
>  ***************
>  *** 828,833 ****
>  --- 828,835 ----
>                 return 0;
>
>         left = tp->snd_cwnd - in_flight;
>  +       if (left >= 65536)
>  +               return 0;
>         if (sysctl_tcp_tso_win_divisor)
>                 return left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd;
>         else
>
>  >
>
>  But it doesn't seem to help (cwnd still grows to 1037).

Cwnd is in packets, not bytes.

Try this series of patches, against net-next.

  -John

View attachment "0001-NET-Allow-send-limited-cwnd-to-grow-up-to-max_bur.patch" of type "text/x-diff" (1231 bytes)

View attachment "0002-NET-Limit-cwnd-growth-when-deferring-for-GSO.patch" of type "text/x-diff" (992 bytes)