[maemo-developers] [maemo-developers] Unreliable Large Network Transfers

From: Simon Moore simon.moore at ndirect.co.uk
Date: Fri Dec 15 11:22:04 EET 2006
Not had any problem with the network as we don't transfer big files.

I think Frantisek might be on to something. We defiantly had the 
problem writing files to the MMC and they don't even have to be 
big.  If you attempt to write data at a significantly faster speed 
than the MMC can actually do, then it just fills up the buffer, so if 
you carry on for a while it looks like it uses all the available 
memory (slowing you down), then in our case the program writing the 
file slowed down and things reached an equilibrium somewhere around 
the point of not really being usable. (we were testing a low level 
driver logging everything to a file).

If you want to prove (although perhaps not conclusively) it is a 
network issue then find some way of transferring the same files but 
don't store them anywhere (e.g. pipe to /dev/null) so it never hits 
the MMC bottleneck, or perhaps put a 250MB file on an MMC and send it 
the other way (although presumably this will be the speed ot the MMC 
bottleneck from the beginning but see if it gets worse).

Shame the drivers are not open source as the others have said, 
because if you do 'prove' it is the wireless driver there is not a 
lot that can be done.  If it is an MMC bottleneck then perhaps best 
to find a way to drop the transfer speed down to that of the MMC 
bottleneck so your device doesn't slow down (also try faster MMC 
cards with the fast drivers, although I'm not sure they are stable yet).


At 07:57 15/12/2006, Frantisek Dufka wrote:

>Mike Lococo wrote:
>>I'm finding that large (>200MB) transfers of data via the wifi 
>>network are extremely unreliable.  They start out running at a 
>>reasonable speed (350KB/sec-600KB/sec), but within a few moments 
>>slow to less than 100KB/sec.  The rates become very erratic, and 
>>the device GUI becomes very unresponsive.
>Are you sure network is a problem? Are you writing data somewhere? 
>Both MMC card and iternal flash are really slow when writing. I had 
>similar problem when writing to MMC card. First it is fast because 
>data is buffered in RAM but then RAM is filled and as you say 'GUI 
>becomes very unresponsive'. You can use 'top' in osso-xterrm to see 
>cpu usage. If it is mmcqd of something like that then it is MMC 
>writing. Enabling multiblock writes helps (a bit experimental feature).
>Only when multiblock writes in MMC driver are enabled then wi-fi 
>driver really becomes a bottleneck. It theory it should be the 
>fastest way how to get data into the device (g wlan does normally > 
>2MB/s speeds) but sadly only ~600kb/s is reality with N770 and 
>current driver. I wonder where exactly the bottleneck wih wi-fi is 
>(hardware of software).
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