Messages in this thread | | | Date | Sun, 15 Mar 2009 21:33:59 -0700 | From | Greg KH <> | Subject | Re: Sierra Wireless (MC8780) HSDPA speed issue |
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On Sun, Mar 15, 2009 at 03:30:54PM -0700, Rory Filer wrote: > Hi Ralf > > Using the driver we sent you on a call-box (i.e. with a "perfect" > simulated network connection) on Ubuntu 8.04 we were seeing ~4 Mbps on > the downlink. So I would rule out any problem with the driver and > conclude it must be something in either PPP/Linux or in the modem. In > order to rule out the modem, I've got a question into one of our UMTS > engineers and will send you a reply when we get the answer. > > We did play around a little with 2.4 kernels of Linux and discovered > there is a buffer in PPP_ASYNC.C which, when its size is increased, > doubled the throughput. If you are savvy enough with Linux, you might > want to try playing with that. We stopped short of any thorough > testing of changing this array size, but were pleased with the result. > If I recall properly, the size of this array is (was, in 2.4) 256 > bytes. Doubling it gave an immediate improvement. We were guessing > that the small size of this buffer was fine in the "old days" when > modems peaked at ~56 kbps. Even 8 years ago that was the fastest you > could go with a GPRS product, now our new HSPA+ products yields 21 > Mbps on Telstra's network! Quite a difference.
Ah, the OBUFSIZE #define in drivers/net/ppp_async.c?
Anyone care to bump this size up and see if that helps out?
thanks,
greg k-h
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