patch for test (Was: tcp_output starving -- is due to mbuf get delay?)

Terry Lambert tlambert2 at
Mon Apr 21 10:26:28 PDT 2003

Borje Josefsson wrote:
[ ... Jin Guojun's TCP output patch for high bandwidth delay product ... ]

> This patch definitively works, and gives much higher PPS (32000 instead of
> 19000). This is on a low-end system (PIII 900MHz with 33MHz bus), I'll
> test one of my larger systems later today.
> One question though - is there any way of having the code being more
> "aggressive"? As You see, in the netstat output below, it takes ~35
> seconds(!) before reaching full speed. On NetBSD I reach maxPPS almost
> immediately. Even if we now (with Your patch) can utilize the hardware
> much more, it only helps if You have connections that lasts for a very
> long time, so that the "ramping" time is not significant.

You can get immediate relief by porting this code instead of
using the patch:

It is for NetBSD 1.3.2, and includes a SACK, Rate Halving,
auto-tuning, and explicit congestion notification:


Direct link to the code:

Also included is a FACK implementation.

-- Terry

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