Messages in this thread | | | Date | Sat, 22 May 1999 16:08:30 +0200 | From | Jochen Heuer <> | Subject | Re: [2.2.9] performance problem on 100MBit network |
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On Fri, May 21, 1999 at 07:23:12PM -0700, Simon Kirby wrote: > 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?
Well, I don't know what happened but at least I can not reproduce it any more. Very strange. Plain 2.2.9 is back to full speed again :) Maybe something else caused this slowdown. I don't know. Maybe it has something to do with my SMC Etherpower II cards. Sometimes I get ping times of up to 20 seconds(!) while normaly ping times are ~0.3ms. If this happens I have to reboot either my server or my client.
What can I do to debug this if it happens again?
Regards,
Jogi
--
Well, yeah ... I suppose there's no point in getting greedy, is there?
<< Calvin & Hobbes >>
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