realloc stack use under O0 for x86_64

[Mike Hommey]

On Thu, Mar 26, 2015 at 12:57:28AM +0000, D'Alessandro, Luke K wrote:
> 
> > On Mar 25, 2015, at 8:34 PM, Jason Evans <jasone at canonware.com> wrote:
> > 
> > On Mar 25, 2015, at 11:48 AM, D'Alessandro, Luke K <ldalessa at indiana.edu> wrote:
> >> We have a lightweight threading system where we are using very small stacks, on the order of 8-32k. We depend on jemalloc for scalable allocation.
> >> 
> >> When we compile jemalloc for debugging purposes, we see realloc using a large amount of stack space:
> >> 
> >> ```asm
> >> 0000000000070e48 <realloc>:
> >>  70e48:       55                      push   %rbp
> >>  70e49:       48 89 e5                mov    %rsp,%rbp
> >>  70e4c:       53                      push   %rbx
> >>  70e4d:       48 81 ec 68 62 00 00    sub    $0x6268,%rsp
> >> ```
> > 
> > Wow, that's far more stack space than I can imagine an explanation for.  What version of jemalloc is this happening with, which OS, compiler, etc.?
> 
> Hi Jason,
> 
> This was with
> 
> jemalloc: 562d266511053a51406e91c78eba640cb46ad9c8
> ./configure CFLAGS="-O0 -g”

Add "-Dalways_inline=" and you'll avoid all the functions that are
forced to be inlined. That might help you.

Mike