Hi All,
As I see in my system, around 4 GB of virtual address space is mapped
to a process. Theoretically, CMIIW, I should be able to use 4GB of
virtual address space.
>From the output from /proc/30563/maps below, there exists a
significant gap or a hole from vma's end address 00978000 to another
vma's start address 08048000. Because of these gaps we'll not be able
utilize complete address space allocated to a process.
***************************************************************************
[bash: /usr2/vskrishn]$ ./test &
[1] 30563
==========================================================================
[bash: /usr2/vskrishn]$
[bash: /usr2/vskrishn]$ cat /proc/30563/maps
00835000-0084a000 r-xp 00000000 08:11 385942 /lib/ld-2.3.4.so
0084a000-0084b000 r--p 00015000 08:11 385942 /lib/ld-2.3.4.so
0084b000-0084c000 rw-p 00016000 08:11 385942 /lib/ld-2.3.4.so
0084e000-00972000 r-xp 00000000 08:11 386926 /lib/tls/libc-2.3.4.so
00972000-00973000 r--p 00124000 08:11 386926 /lib/tls/libc-2.3.4.so
00973000-00976000 rw-p 00125000 08:11 386926 /lib/tls/libc-2.3.4.so
00976000-00978000 rw-p 00976000 00:00 0
08048000-08049000 r-xp 00000000 00:1e 2191602 /usr2/vskrishn/test
08049000-0804a000 rw-p 00000000 00:1e 2191602 /usr2/vskrishn/test
b7ff2000-b7ff3000 rw-p b7ff2000 00:00 0
bff69000-c0000000 rw-p bff69000 00:00 0
ffffe000-fffff000 ---p 00000000 00:00 0
===========================================================================
[bash: /usr2/vskrishn]$ pmap 30563
30563: ./test
00835000 84K r-x-- /lib/ld-2.3.4.so
0084a000 4K r---- /lib/ld-2.3.4.so
0084b000 4K rw--- /lib/ld-2.3.4.so
0084e000 1168K r-x-- /lib/tls/libc-2.3.4.so
00972000 4K r---- /lib/tls/libc-2.3.4.so
00973000 12K rw--- /lib/tls/libc-2.3.4.so
00976000 8K rw--- [ anon ]
08048000 4K r-x-- /usr2/vskrishn/test
08049000 4K rw--- /usr2/vskrishn/test
b7ff2000 4K rw--- [ anon ]
bff69000 604K rw--- [ stack ]
ffffe000 4K ----- [ anon ]
total 1904K
[bash: /usr2/vskrishn]$
**********************************************************************
can any one help me out with
What are these gaps for?
why are those gaps formed?
Is there any way to optimize/reduce those gaps?
any reference to text/source which can clarify would be helpful too?
I hope the gap at the end refers to the Heap, so not bothered much about it.
thanks
-kris
PS: test.c
#include <stdio.h>
#include <stdlib.h>
int main()
{
sleep(30);
}
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