Linux scheduler, overscheduling performance, threads

[Alan Cox]

> Thousands of threads in a program is not unreasonable.  If you may want to

More than a couple of threads per CPU is highly unreasonable.

> take full advantage of a 128 CPU machine, for example, you need _at_
> _least_ 128 threads.  If your threads spend most of their time blocking,

Linux doesnt run on any 128 CPU machines, so it would be bad to tune for  it.
You want 256 threads on a 128 cpu box, ok no argument

> desktop/small server OS out there. But if Linux is going to play in the
> enterprise market- running the same programs and doing the same jobs
> (albeit slower and cheaper) as that Enterprise 10000 server, it had better
> be ready to deal with applications that spawn thousands of threads.

And what happens when someone comes along with a performance issue. Do you
try and cope with excessive threads, 20Mb of kernel overhead, trashed
caches or do you put your thinking hat on. In java you have very poor AIO
facilities which doesnt help (I believe the newest java stuff fixes this ?)

Alan


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