Re: Priority, Speed

On Apr 27, 2006, at 01:39, Florin Braghis wrote:

> Thanks for the answers, Arvid!
>
> > > b) Downloads between two peers won't go faster than 1Mb/s  - is  
> > > it  a limitation built into the library ?
> > I presume you mean 1 MB/s, that is also the download speed I get  
> > at  most. Slightly about 1 MB/s, but that's the hard limit on my  
> > internet connection as well.
>
> > Maybe it's the download buffer size. Are you testing on a LAN  
> > with  one other peer? trying to push the speed for a single  
> > connection?
>
> I'm on a 100Mbps LAN. 1 client trying to download from 1 client.  
> Both clients are in debug build (Windows).
> I don't think it's the hard disk limit - the computers are fairly  
> fast and I get up to 7MB/sec with other BT clients from the internet.
>
> I'll get the latest cvs update and see if the problem still persists.

The limiting factors are the number of outstanding requests sent to  
the peer. In order to reach to about 2 MB/s, the client has to be  
configured to send about 200 outstanding requests to peers. Some  
peers will start to ignore requests when they reach about 50  
outstanding requests. The default in libtorrent right now is 48 (it's  
a constant in policy.hpp). That is the factor that limits the top speed.

The "acceleration" of the download speed is controlled by a constant  
called request_queue_time in session_settings.hpp (this file is new,  
and you may need today's snapshot to have it. The class can be found  
inside session.hpp in older versions). This constant controls the  
relationship between the outstanding request queue size and the  
download rate. The former is controlled by the latter, and the time  
is the time it should take for the other end to transfer all the  
requests in the queue with the current download rate. The higher this  
time is, the faster the speed will increase and reach the saturation  
point.

The session_settings class is a start in making all of these  
constants configurable from the API, they will be made configurable.

Hope this is to any help.


--
Arvid Norberg




-------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642