lpsm_zalloc

[H. Peter Anvin]

Stephan Engström wrote:
> Hi!
> 
> First I must say that this project is really, really welcomed here. I
> have been looking for this a long time and even began coding something
> like this, but I just had too many questions regarding portability and
> other troubles.
> If Peter has massive amount of time to spare I would really like some
> more information on the following:
> 
> - Can this project ever be portable to, let's say, Solaris?

"Portable" probably not, "ported" probably.  What I mean with that is 
that it's probably going to require Solaris-specific code to be added. 
Now, that's not really a huge tragedy, but it's not going to be my main 
focus.

> - This fixed adress that the PM attaches to, how safe it is and in what
> conditions can it fail?

It's pretty safe.  The main reason it would fail is due to very large 
mmap()s (more than a few hundred MB) in use at the same time.

> - Is it possible to share the PM among processes?

No.  I have been thinking about how to possibly make it thread-safe, but 
making it shared between processes seems almost impossible.

> Anyway, I wanted to test and benchmark the clever lpsm_zalloc() and it
> doesn't work very well, I get a segfault when the first buddy allocation
> is called.
> I use v 0.1.5.
> 
> In zalloc.c the mmap call return -1 (ENODEV), when I try to add the
> MAP_ANONYMOUS flag to mmap the program segfaults a couple of hundred
> times and then dies. Thats how far I came.

Not too good :(  I'll have to look at it and get it fixed.  Probably have 
to write another test program... those darned test programs seem to be 
finding all kinds of bugs... :-)

	-hpa