Silas Boyd-Wickizer:
> > Why do you believe that this should use 100% of ALL Cpus?
> >
> > If you look at your synthetic test then you will likely find that
> > there are at any point in time only a few mail receiving processes
> > and mail delivering processes, and that these processes will all
> > be waiting for kernel system calls to complete.
> >
> > With this synthetic test you really have only a low-concurrency load.
>
> Yes, there are only a few mail delivering processes (virtual).
> Why is this a function of my load? There are many messages
> waiting for delivery, so why doesn't postfix run more virtuals
> to increase concurrency?
One Postfix process uses one CPU at any point in time. The Postfix
scheduler is one such process. You have clocked this process at
300 microseconds per message. Congratulations. You will never have
a real network or real file system that can sustain this. So now
you can focus on real problems instead.
> I'm not sure what you mean by "waiting for kernel system calls to
> complete". Do you mean "executing kernel system calls" (reading
> from a pipe), or "blocked on kernel system calls" (i.e. waiting
> on a pipe)?
Kernels execute system calls. Processes can only ask and wait
while the kernel is doing kernel thingies.
Wietse
