Christian Schmid wrote:

bert hubert wrote:

quoted

On Mon, Feb 21, 2005 at 01:35:33AM +0100, Christian Schmid wrote:

Outgoing data. I am using sendfile() to send the file on a non-blocking 
socket but the call blocks for 100 ms per socket if I get over 3000 
sockets. Thats causing the massive slowdown in sum. I first thought its 
a disk-issue but I tried with pure-cache data as well and it still blocks.

quoted

quoted

3000 sockets = no slowdown at all (500 MBit in use)
3300 sockets = 10% slowdown
3600 sockets = 30% slowdown
4000 sockets = 60% slowdown (i aborted here, as it only uses 200 MBit 
for sending... catastrophy!)

[snip]

quoted

I'm a bit confused, it is a download service so you are probably 
*sending*
data? 

Only sending. Receiving ACKs of course.

I've been doing some work to improve ACK performance, you can find some 
patches for Linux 2.6.6 at http://hamilton.ie/net/

I've only tested these patches for a single (or few) very fast 
connections, but I'd expect the problem might manifest itself for a very 
large number of connections as well. Though then you might hit other 
bottlenecks (memory access for different structures).

Baruch