[cacao] mmap first page

[Michael Starzinger]

Hello!

With the latest changeset [1] I finally disabled the mmap of the first  
page in our trap handling code by default. Note that this also  
obsoletes IcedTea's 'cacao-no-mmap-first-page' patch.

On 19.05.2009, at 10:51, Michael Starzinger wrote:
> 1) If removing the mapping increases the number of systems that CACAO
> runs on out of the box, we should do it. The problem is, I cannot
> remember which (how many) systems there are which need this explicit
> mapping. Can anyone comment on this?

This is still true. I strongly suspect that this changeset breaks  
Cacao for Solaris but I cannot verify that. It would be great if  
someone could confirm/deny my suspicions. Here is how to fix it  
correctly. For those arch/OS combinations which need the mmap, set the  
global opt_AlwaysMmapFirstPage flag to true in the appropriate  
md_init() function. To find out if you need the mmap, just run  
extest.java or any other Java application which throws implicit null  
pointer exceptions.

> 3) I still want to have the code available for testing purposes. So I
> don't want to remove it completely. My suggestion would be something
> like -XX:+MmapFirstPage (better name required) which allows to easily
> test this for debug-enabled builds.

The switch is called -XX:+AlwaysMmapFirstPage (the name just doesn't  
get better) and can be used for debugging purposes.

PS: Sorry for the (extremely long) delay. I totally forgot about the  
issue until it hit me yesterday on one of our machines after a system  
update.

References:
[1] http://mips.complang.tuwien.ac.at/hg/cacao/rev/52906d568dba

-michi