[linux-elitists] USB-Serial and pppd

Greg KH greg@kroah.com
Thu Jun 12 16:32:47 PDT 2008

On Thu, Jun 12, 2008 at 03:45:25PM -0400, Greg Folkert wrote:
>         linux-image-2.6.25-2-686-bigmem v2.6.25-4
>         linux-image-2.6.24-1-686-bigmem v2.6.24-6

That's good, but you should update your .24 one to .25 to make sure.

> I use the 2.6.24 kernel as ACPI/APM/CPUFREQ is screwed up on the 2.6.25
> kernel, I only get 800MHz out of this laptop with the 2.6.25 kernel
> running along with the cpu frequency scaling stuff.

You might want to just turn that off then :)

> I had an extended stint in a colo in Denver about 300ft away from a
> Verizon Cell tower and only got 512K/sec in Linux period, the guy next
> to me had a MacBookPro with a ExpressCard model and same 512K results
> came along in my Lenovo using that card. He gets hyarge throughput on
> his MacBookPro compared to my T61. I tried on 2.6.24 only as I hadn't
> had the time to update to 2.6.25 when it came out. But now it gives
> similar results.

Ok, I can't understand what you are saying here, is it that you got
512K/second just like someone else using os-x did?  If so, what is the

Also note, I forgot to mention this the first time, but some people's
data plans cap the throughput to a specific level.  I proved this to
someone by using my card in their laptop with the exact same driver and
device type.  My data plan has no caps, his did.

So, you might want to check with your phone company :)

> And its frustrating, but I'm in this for the long haul no matter what
> SCOg thinks, or what Law.com mis-believes about the GPL and IP. Or wrong
> thinking/attacks by Microsoft.

And this is related to throughput of a driver how?  Please...

Ok, please measure up and down throughput separately, as they are very
different.  If you can rebuild your kernel, here's some things you can
try to change these numbers.

In the file, drivers/usb/serial/sierra.c, make sure that the buffer
sizes and numbers all show:
	#define N_IN_URB        4
	#define N_OUT_URB       4
	#define IN_BUFLEN       4096

If not, increase them to those levels.

If they are set to those levels, then you can try to increase the number
of URBs from 4 to 8, but it's usually a level of diminishing returns,
the network is usually too slow that you really need more than that big
of a buffer in flight at once.

But try it and let me know what happens.  And use 2.6.25, no one cares
about 2.6.24 anymore :)


greg k-h

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