Re: incorrect malloc_stats output

[wmglo]

Hi,

> Once Arena 0 reaches its limit of 1GB (TASK_UNMAPPED_BASE) malloc_stats
> output shows a large incorrect value (1.54Gb) for system bytes and in use
> bytes (which affects Total). The actual total memory usage here is about
> 1.5 - 1.6Gb (as reported by top) instead of 2.1gb.
...
> Secondly, the memory does seem to be allocated from main arena (sbrk'ed?)
> although TASK_UNMAPPED_BASE is supposed to limit it to 1GB. What is
> happening here ?? I ran a simple single threaded program that continually
> allocates memory and found main arena could exceed 1GB. Is that expected ?

Yes, _this_ is expected.  First, foreign sbrk()s are counted as system
memory:

      /* Count foreign sbrk as system_mem.  */
      if (old_size)
        av->system_mem += brk - old_end;

Second, the main arena can also be extended beyond TASK_UNMAPPED_BASE
using mmap.  This is a feature of Doug Lea's malloc-2.7.0 which I did
not disable.  So, the main arena can exceed 1GB.

> However, the above is independent of the bug. malloc_stats actually ends
> up  going to 4.5GB or so on my 4GB box. The Total below of 3.67Gb is 
> ridiculous as user space ends at 3GB. 

_That_ indeed looks bogus.  Can you send me your test program?

Thanks,
Wolfram.