Groups > comp.os.linux.development.system > #265

[Linux] malloc: small size - small pointer?

From	Alex Vinokur <alex.vinokur@gmail.com>
Newsgroups	comp.os.linux.development.system, comp.unix.programmer
Subject	[Linux] malloc: small size - small pointer?
Date	2011-09-13 01:17 -0700
Organization	http://groups.google.com
Message-ID	<c36c7bc2-537d-4f24-976f-c08d61e06bb6@w12g2000yqa.googlegroups.com> (permalink)

Cross-posted to 2 groups.

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Hi,



Linux 2.6.18-238.1.1.el5 #1 SMP Tue Jan 4 13:32:19 EST 2011 x86_64
x86_64 x86_64 GNU/Linux

Intel(R) C++ Intel(R) 64 Compiler XE for applications running on
Intel(R) 64, Version 12.0.4.191 Build 20110427


malloc() returns "small" pointers for small sizes.
Any suugestions for such behavior of the malloc function.

Are "small" pointers on heap?



------- Program foo.cpp -------
#include <stdio.h>
#include <stdlib.h>

#define SHOW(s_i_z_e, p_o_i_n_t_e_r) printf ("Size = 0x%lx, Pointer =
%p\n", s_i_z_e, p_o_i_n_t_e_r)

int main()
{
	size_t size = 0x1ffe0;
	void* pointer = 0;

	for (size_t i = 0; i < 0x10; i++)
	{
		pointer = malloc(size);
		SHOW(size, pointer);
		size++;
  }

  return 0;
}

-------------------------------



Compilation:
> icpc foo.cpp


Running:

> ./a.out

Size = 0x1ffe0, Pointer = 0x199cc010
Size = 0x1ffe1, Pointer = 0x199ec000
Size = 0x1ffe2, Pointer = 0x19a0bff0
Size = 0x1ffe3, Pointer = 0x19a2bfe0
Size = 0x1ffe4, Pointer = 0x19a4bfd0
Size = 0x1ffe5, Pointer = 0x19a6bfc0
Size = 0x1ffe6, Pointer = 0x19a8bfb0
Size = 0x1ffe7, Pointer = 0x19aabfa0
Size = 0x1ffe8, Pointer = 0x19acbf90
Size = 0x1ffe9, Pointer = 0x19aebf80
Size = 0x1ffea, Pointer = 0x2ae67b770010
Size = 0x1ffeb, Pointer = 0x2ae67b791010
Size = 0x1ffec, Pointer = 0x2ae67b7b2010
Size = 0x1ffed, Pointer = 0x2ae67b7d3010
Size = 0x1ffee, Pointer = 0x2ae67b7f4010
Size = 0x1ffef, Pointer = 0x2ae67b815010


Alex

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Thread

[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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