Derek Simkowiak wrote:
>
> The serial ports are character devices (unbuffered) under Linux. I
> don't know if there is any equivalent to the Windows setting or not.
>
> I couldn't find anything about it in the setserial or pppd man
> pages, so I'm guessing it does not apply.
>
> --Derek
>
> On Tue, 30 Nov 1999, Hoyt wrote:
>
> > A while back, MaximumPC magazine featured an article on tweaking the Windows
> > dial up connection. They worked great for me on my Windows box and, after
> > doing some research, were implemented successfully on my Linux boxes.
> > Essentially, they are:
> >
> > 0. A long description in the article on how to determine the optimum mtu.
> > 1. Set mtu and mru in /etc/ppp/options to 576 (or use ifconfig ppp0 mtu
> > 576).
> > 2.Set mss and rwin: route add default gw <ip assigned by your isp> mss 536
> > window 2144.
> > 3. Turn off IP header compression in /etc/ppp/options using the novj optin.
> > 4. Add %C0 and %E0 to modem init string, turning off MNP5 compression and
> > auto retrain.
> >
> > You can look at the respective man pages for details.
> >
> > One tweak (not from the article, BTW) I cannot figure out how to implement
> > is one which increases the cache for the modem. The Windows tweak is as
> > follows:
> >
> > "Modems have a relatively small on-board cache and data buffer. The
> > following settings allow the modem to access some of the system RAM to use
> > as cache during times of high modem activity. Go into your system.ini file.
> > Locate the following: [386Enh]
> >
> > If your modem is on Com 1, on the line directly below the [386Enh] add this:
> >
> > Com1Irq4Buffer=1024
> >
> > If your modem is on Com 2, on the line directly below the [386Enh] add this:
> >
> > Com2Irq3Buffer=1024
> >
> > If your modem is on Com 3, on the line directly below the [386Enh] add this:
> >
> > Com3Irq4Buffer=1024
> >
> > If your modem is on Com 4, on the line directly below the [386Enh] add this:
> >
> > Com4Irq3Buffer=1024 "
> >
> > This tweak resulted in a significant improvement for my Windows box. Any
> > ideas on how to implement it in Linux?
> >
> > Thanks,
> > Hoyt
> >
> >
> >
There is one other thing you can do to pump up PPP in linux. The serial device
interrupts have priority 11 and 12 in the normal setup of the kernel. Since this
may result in a delay while higher-priority Interrupt Service Routines are in
their interrupt masking, the frame could be dropped, resulting in a repeat TCP/IP
packet.
http://www.best.com/~cae/irqtune
has a dynamic patch that reassigns the priorities of the ISR stack. Careful use
and appropriate experimentation can result in a system with higher performance,
not always, but many times.
Civileme
