On Sat, 23 Apr 2011 23:19:53 -0400
Ken Wesson <kwess...@gmail.com> wrote:
> On Sat, Apr 23, 2011 at 8:13 PM, Mike Meyer <m...@mired.org> wrote:
> > On Sat, 23 Apr 2011 19:41:28 -0400
> > Ken Wesson <kwess...@gmail.com> wrote:
> > or you live in a universe where cosmic rays can flip bits and other
> > sources of hardware hiccups exist.
> Software crashes caused by non-software-bug-triggered memory
> corruption seem to me to be exceedingly rare, and they could as easily
> strike critical parts of the operating system as a multithreaded
> server program (and a large batch of independent C jobs will occupy
> more memory and have a correspondingly larger cross section as a
> target for such things).
> The best recourse if the server gets hit by something like that is
> going to be to reboot it.
While it might be exceedingly rare on a per-cpu-second basis, if your
application runs 7x24 on enough cpus, you can expect to see them at
regular intervals. In which case the best recourse - if you want a
stable, robust application - is to restart the smallest set of
processes that might have been affected by the problem. In some cases,
that is the server. In others, it's a single process. In still others,
it's the set of servers participating in a distributed application.
> >> > starting a pool of processes to avoid the startup time of a new process
> >> > when a new client connects.
> >>
> >> With small lightweight C processes and some suitable system for IPC,
> >> this can work. With JVMs, not so much, unless you have RAM coming out
> >> of your ears. JVM processes tend to be fairly large; it wouldn't take
> >> many 64MB java.exe jobs to start the pagefile thrashing. Even with an
> >> 8GB server, you start paging at 128 simultaneous connections in that
> >> case, and you certainly can't handle thousands.
> >
> > I would have expected large chunks of the JVM processes to be shared
> > between parent and child - especially before the first accept
> > returns.
>
> That happens forking C programs. It won't happen starting up separate,
> independent JVM processes, and I don't know how a JVM will handle it
> if a native method calls fork() but I somehow doubt it will all just
> work peachily.
Ah, good point. I don't think in Java, so forget that it doesn't
necessarily have access to all the facilities of the underlying OS.
<mike
--
Mike Meyer <m...@mired.org> http://www.mired.org/consulting.html
Independent Software developer/SCM consultant, email for more information.
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