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Re: [Linux] malloc: small size - small pointer?

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On 09/13/2011 10:17 AM, Alex Vinokur wrote:
> malloc() returns "small" pointers for small sizes.
> Any suugestions for such behavior of the malloc function.
> Are "small" pointers on heap?

 From the Linux glibc man page:

"Normally, malloc() allocates memory from the heap, and adjusts the size 
of the heap as required, using sbrk(2).  When allocating blocks of 
memory larger than MMAP_THRESHOLD bytes, the glibc malloc() 
implementation allocates  the  memory  as  a  private anonymous mapping 
using mmap(2).
MMAP_THRESHOLD is 128 kB by  default,  but  is  adjustable  using 
mallopt(3).   Allocations  performed  using  mmap(2) are unaffected by 
the RLIMIT_DATA resource limit (see getrlimit(2))."

In your test, malloc switched to mmap after $[0x1ffea] == 131050 == 
roughly 128KiB.

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[Linux] malloc: small size - small pointer? Alex Vinokur <alex.vinokur@gmail.com> - 2011-09-13 01:17 -0700
  Re: [Linux] malloc: small size - small pointer? Xavier Roche <xroche@free.fr.NOSPAM.invalid> - 2011-09-13 10:23 +0200
    Re: malloc: small size - small pointer? Alex Vinokur <alex.vinokur@gmail.com> - 2011-09-13 23:21 -0700
    Re: malloc: small size - small pointer? Alex Vinokur <alex.vinokur@gmail.com> - 2011-09-13 23:18 -0700
      Re: malloc: small size - small pointer? Alex Vinokur <alex.vinokur@gmail.com> - 2011-09-14 00:08 -0700
  Re: [Linux] malloc: small size - small pointer? Kaz Kylheku <kaz@kylheku.com> - 2011-12-24 06:56 +0000

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