60KB Shared library memory on /proc/<pid>/maps

yaniv levy sbscrb at gmail.com
Mon Feb 16 10:21:23 EST 2015


Hi,

In a quest for understanding RAM requirements of system processes, I
arrived to analysis of /proc/<pid>/maps.

I have noticed that many shared libraries have exactly 60KB space allocated
in virtual memory right after the code, with permissions "---p", meaning
non-executable, non-writable, non-readable and private.

My guess is that it is not the .text .data or .bss sections of the shared
library because it is not r/w/x.

What is it? can it be reduced?

When using /proc/<pid>/smpas to further dive in,  I haven't seen it in RSS
(Resident Memory), so one can claim that it is of no importance to RAM use.

I tried to relate it to the executable or shared library sections by using
objdump or readlef, but I could not find a section that's 60KB.

For example:
76d2d000-76d94000 r-xp 00000000 1f:00 439        /lib/libc.so.0
76d94000-76da3000 ---p 00000000 00:00 0     (What's that?)
76da3000-76da4000 r--p 00066000 1f:00 439        /lib/libc.so.0
76da4000-76da5000 rw-p 00067000 1f:00 439        /lib/libc.so.0
76da5000-76dab000 rw-p 00000000 00:00 0


Thank you
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