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SubjectRe: [2.2.9] performance problem on 100MBit network
On Thu, 20 May 1999, Jochen Heuer wrote:

> using 2.2.9 on my server or my client brings down the performance
> on my local network. I'm using SMC Etherpower II on both machines
> which are connected via a 100MBit hub.
>
> Using ftp the transferrates drop to ~200 k/s (>6 M/s with 2.2.8).
> If I revert the following part of patch-2.2.9 the network runs at
> full speed again:
>
> diff -u --recursive --new-file v2.2.8/linux/include/net/tcp.h linux/include/net/tcp.h
> --- v2.2.8/linux/include/net/tcp.h Tue May 11 13:10:32 1999
> +++ linux/include/net/tcp.h Thu May 13 10:33:17 1999
> @@ -728,7 +728,7 @@
> */
> extern __inline__ __u32 tcp_recalc_ssthresh(struct tcp_opt *tp)
> {
> - __u32 snd_wnd_packets = tp->snd_wnd / tp->mss_cache;
> + __u32 snd_wnd_packets = tp->snd_wnd / max(tp->mss_cache, 1);
>
> return max(min(snd_wnd_packets, tp->snd_cwnd) >> 1, 2);
> }
>
>
> What is the reason behind this patch or can I tune my system
> using /proc/sys/net ?

This cannot be possible unless a compiler is breaking something here.
What you are reverting avoids a possible division by zero -- the only way
it could have been faster before was if it was spitting out divison by
zero errors and still going. Are you changing anything else between
kernels?

Simon-

| Simon Kirby | Systems Administration |
| mailto:sim@netnation.com | NetNation Communications |
| http://www.netnation.com/ | Tech: (604) 684-6892 |


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