linux-kernel - Big reserved mappings on x86

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Date:	Wed, 25 Apr 2007 10:42:20 +0200 (MEST)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Big reserved mappings on x86_64

Hello,


I noticed that on x86_64, the VSZ indicator (`ps u $$`) is quite high, 
compared to i386 or sparc64.

10:32 ichi:~ > ps u $$ # i686
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
jengelh   4950  0.2  0.2   4776  2112 pts/4    Ss   10:32   0:00 -bash
10:36 sun:~ > ps u $$ # sparc64
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
jengelh  17842  0.0  0.0   6320  1960 pts/0    Ss   10:36   0:00 -bash
10:36 opteron:~ > ps u $$ # x86_64
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
jengelh   4403  0.0  0.2  23808  2632 pts/3    Ss   10:27   0:00 -bash

I actually took a look at `pmap $$`, which reveals that a lot of shared 
libraries map 2044K or 2048K unreadable-unwritable-private 
mappings...for _what_ purpose?

10:37 opteron:~ > pmap $$
4403: bash
START       SIZE     RSS   DIRTY PERM MAPPING
2ae6cca70000    212K    172K      0K r-xp /lib64/libreadline.so.5.2
2ae6ccaa5000   2044K      0K      0K ---p /lib64/libreadline.so.5.2 <--
2ae6ccca4000      4K      4K      4K r--p /lib64/libreadline.so.5.2
2ae6ccca5000     28K     28K     28K rw-p /lib64/libreadline.so.5.2
2ae6cccac000      8K      8K      8K rw-p [anon]
2ae6cccae000     28K     16K      0K r-xp /lib64/libhistory.so.5.2
2ae6cccb5000   2048K      0K      0K ---p /lib64/libhistory.so.5.2 <--
2ae6cceb5000      8K      8K      8K rw-p /lib64/libhistory.so.5.2
2ae6cceb7000    320K    208K      0K r-xp /lib64/libncurses.so.5.5
2ae6ccf07000   2048K      0K      0K ---p /lib64/libncurses.so.5.5 <--
2ae6cd107000     48K     48K     48K r--p /lib64/libncurses.so.5.5
2ae6cd113000     28K     28K     28K rw-p /lib64/libncurses.so.5.5
[...]

What could these ominous mappings be? Does anyone else see that - 
perhaps someone with x86_64 && !(opensuse 10.2)?


Jan
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