Re: Subtle MM bug

[Linus Torvalds]

In article <[e-mail]>,
Andrea Arcangeli  <[e-mail]> wrote:
>On Mon, Jan 08, 2001 at 03:22:44PM -0800, Wayne Whitney wrote:
>> I guess I conclude that either (1) MAGMA does not use libc's malloc
>> (checking on this, I doubt it) or (2) glibc-2.1.92 knows of these
>> variables but has not yet implemented the tuning (I'll try glibc-2.2) or
>> (3) this is not the problem.
>
>You should monitor the program with strace while it fails (last few syscalls).
>You can breakpoint at exit() and run `cat /proc/pid/maps` to show us the vma
>layout of the task. Then we'll see why it's failing.  With CONFIG_1G in 2.2.x
>or 2.4.x (confinguration option doesn't matter) you should at least reach
>something like 1.5G.

It might be doing its own memory management with brk() directly - some
older UNIX programs will do that (for various reasons - it can be faster
than malloc() etc if you know your access patterns, for example).

If you do that, and you have shared libraries, you'll get a failure
around the point Wayne sees it. 

But your suggestion to check with strace is a good one.

		Linus