SV: SV: SV: Multiple cpu?

[Jim Levie]

On Wed, 2002-09-18 at 09:25, Julian Field wrote:
> At 15:11 18/09/2002, you wrote:
> >  Child processes do their work and exit so that they don't needless
> >consume resources. At least that's what I assume Julian has done.
>
> They run for a few hours then die and are restarted by the master.
>
While that's not the classical master/child scenario it probably does
make more sense for MailScanner. The startup cost of a child in this
case is not insignificant. So it does make more sense to start up the
children and leave them running.
>
> > > You all probably figured out my level of expertice  =(
> > > but this is something I relly need to understand.
> > > My guess from the begining was thats with 2 cpu MS would be
> > > able to scan faster. But know Im not sure If I should spend the
> > > extra money.
> > > Does 2 cpu demands extra config or will it handle it by it self?
> > >
> >You won't gain much advantage as far as MS is concerned from a
> >multi-processor box. However, MS isn't the only thing active on a system
> >that also happens to be running MS, so the other processor will get used
> >but things like the sendmail and other tasks the system runs. My
> >personal recommendation is to go with a multi-processor if you have a
> >significant mail load.

Now that I read what I had written above I think I should clarify what I
meant. The current V3 code won't take full advantage of a
multi-processor unless you arrange for multiple instances of MS. The
system as a whole will take advantage of multiple CPU's, so a
multi-processor box is a "good thing" if you have significant load. And
it's the expected load that really determines the need for a dual
processor box.

One other thing to consider... There's a fair bit of IO in something
like MS. So it does make since to have more than one MS process active
on a uni-processor box, providing you don't run the system out of
memory. Very informal testing on my part indicates that 2 or 3 instances
of MS seem to be the "sweet spot', depending somewhat on the disk I/O
speed and the content of the mail stream. There's enough idle time from
disk I/O that a second or third MS can take advantage of that idle time
for compute work.
--
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The instructions said to use Windows 98 or better, so I installed RedHat
   Jim Levie                                 email: jim at entrophy-free.net