[svlug] Re: Thread Programming part 2

[Tin Le]

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On Mon, 5 Jun 2000, Karen Shaeffer wrote:

> > As it is currently, Linux does not have kernel support for many-to-many
> > threading.  See
> > 
> > http://www-4.ibm.com/software/developer/library/java2/index.html
> > 
> > for a pretty good discussion.  I know there are people in the Linux
> > developers group who disagreed with it.  As I said, it is deeply
> > religious ground.

> > Tin Le
> ---end quoted text---

> Well, I've read some of the more recent _threads_ on lkl concerning this
> issue of many-to-many threads. I'm just a casual observer, but it seems that
> those involved with the linux kernel have no interest in optimizing the
> kernel for java applications. Concerning your comments about clones needing
> additional support inside the os, the thinking is that this additional
> support is best provided in userspace rather than in the kernel--because
> many other applications would take a performance hit, for the sake of the
> special case applications that would benefit from providing kernel level
> support for many-to-many threads.

> I don't think it's a religious issue at all. I think they have
> demonstratable performance numbers to support these views. It's really a
> question of whether you want to cater to the Java crowd at the expense of
> others. These are just my casual observations, and they may not be
> completely accurate... I have no personal opinion on the matter.

You are right.  Nothing comes for free.  Tuning the kernel for Java would
mean something else run slower.  That's the way it is.  You can't have a
kernel that is the fastest in all area.

I agree 100%.  It just means that thread on Linux is not going to be as
fast as threads in Solaris.  Also mean that thread on Linux will have other
limitations.  That was the point I was trying to make.  Probably went too
far on the "religious" point, sorry :-).  Although being inflexible could
be construed as....

I've heard of some talk of making the VM and scheduler in Linux modular,
i.e. easy to drop in a different VM and sched.  That might be the solution
for Java on Linux.  Allow people to run the VM and sched that is optimized
for their app.

Hmm, maybe Linux on a microkernel (Mach anyone?) would be the solution...
;-)

Tin Le
- ----
http://tin.le.org
Internet Security and Firewall Consulting
Tin Le - tin at le.org

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