Messages in this thread | | | Date | Mon, 07 Mar 2005 02:58:32 +0100 | From | Christian Schmid <> | Subject | Re: BUG: Slowdown on 3000 socket-machines tracked down |
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Ben Greear wrote: > Christian Schmid wrote: > >> Hello. >> >> After weeks of work, I can now give a detailed report about the bug >> and when it appears: >> >> Attached is another traffic-image. This one is with 2.6.10 and a 3/1 >> split, preemtive kernel, so all defaults. > > > What are the units on your graph. You say "MB" several places, but > do you mean Mb (ie, Mega-bit) instead?
The unit on this graph is kilobytes. So 80000 there means 80 megabytes per second.
> I have a tool that can also generate TCP traffic on a large number of > sockets. If I can understand what you are trying to do, I may be able > to reproduce the problem. My biggest machine at present has only > 2GB of RAM, however...not sure if that matters or not.
It should not matter. Low-memory is both just 1 GB if you have default 32 bit with 3/1 split.
> Are you sending traffic in only one direction, or more of a full-duplex > configuration?
Its a full-duplex. Its a download-service with 3000 downloaders all over the world.
> Is each socket running the same bandwidth?
No. It ranges from 3 kb/sec to 100 kb/sec. 100 kb/sec is the limit because of the send-buffer limits.
> What is this bandwidth?
1000 MBit
> Are you setting the send & rcv buffers in the socket creation > code? (To what values if so?)
Yes. send-buffer to 64 kbytes and receive buffer to 16 kbytes.
> How many bytes are you sending with each call to write()/sendto() whatever?
I am using sendfile-call every 100 ms per socket with the poll-api. So basically around 40 kb per round.
> Is there any significant latency between your sender and receiver machine? > If so, how much?
3000 different downloaders, 3000 different locations, 3000 different machines ;)
> What is the physical transport...GigE? 1500 MTU?
Yes.
Chris
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