Linux Tutorials - Herong's Tutorial Examples - v5.45, by Herong Yang
/proc/{id}/maps - Process Memory Map
This section describes the pseudo file '/proc/{id}/maps' that represents virtual memory map of a given process.
What Is /proc/{id}/maps? - /proc/{id}/maps is a pseudo file that contains the memory map of the process of the given id.
Here is the memory map for process ID 1998 retrieved from the /proc/1998/maps pseudo file.
herong$ sudo cat /proc/1998/maps 561c0ddea000-561c118f7000 r-xp 00000000 fd:00 36252107 /usr/libexec/mysqld 561c118f7000-561c11a6c000 r--p 03b0c000 fd:00 36252107 /usr/libexec/mysqld 561c11a6c000-561c11df3000 rw-p 03c81000 fd:00 36252107 /usr/libexec/mysqld 561c11df3000-561c12320000 rw-p 00000000 00:00 0 561c1403c000-561c18d6a000 rw-p 00000000 00:00 0 [heap] 7ff838000000-7ff83a455000 rw-p 00000000 00:00 0 7ff83a455000-7ff83c000000 ---p 00000000 00:00 0 ... 7ff90b6d5000-7ff90b6d6000 r--p 0002c000 fd:00 46923995 /usr/lib64/ld-2.28.so 7ff90b6d6000-7ff90b6d8000 rw-p 0002d000 fd:00 46923995 /usr/lib64/ld-2.28.so 7ffcf9398000-7ffcf93b9000 rw-p 00000000 00:00 0 [stack] 7ffcf93da000-7ffcf93dd000 r--p 00000000 00:00 0 [vvar] 7ffcf93dd000-7ffcf93df000 r-xp 00000000 00:00 0 [vdso] ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]
The output fields in each line are described below:
start-end perm offset major:minor inode image
where:
start - The starting address of the mapped virtual memory area.
end - The ending address of the mapped virtual memory area.
perm - A 4-bit mask with the first three bits representing process
r (read), w (write) and x (execute) permissions for the
area. The last bit is process ownership of the area:
p (private) or s (shared).
offset - The offset in the file where is area is mapped to.
major - The major number of the device holding the mapped-to file.
minor - The minor number of the device holding the mapped-to file.
inode - The inode number of the mapped-to file.
image - The name of the mapped-to file.
Compare "/proc/{id}/maps" and "pmap" Reports - Looking at their outputs, the "pmap" command seems to be using the "/proc/{id}/maps" pseudo file to generate report. Let's confirm this with a simple process, "sleep".
herong$ sleep 600000000 & 649848 herong$ sudo pmap -x 649848 649848: sleep 600000000 Address Kbytes RSS Dirty Mode Mapping 000056392fc85000 28 28 0 r-x-- sleep 000056392fe8c000 4 4 4 r---- sleep 000056392fe8d000 4 4 4 rw--- sleep 0000563931dd7000 132 24 24 rw--- [ anon ] 00007f47dc913000 2740 192 0 r---- LC_COLLATE 00007f47dcbc0000 1776 1216 0 r-x-- libc-2.28.so 00007f47dcd7c000 2044 0 0 ----- libc-2.28.so 00007f47dcf7b000 16 16 16 r---- libc-2.28.so 00007f47dcf7f000 8 8 8 rw--- libc-2.28.so 00007f47dcf81000 16 12 12 rw--- [ anon ] 00007f47dcf85000 176 172 0 r-x-- ld-2.28.so 00007f47dd149000 332 128 0 r---- LC_CTYPE 00007f47dd19c000 4 4 0 r---- LC_NUMERIC 00007f47dd19d000 4 4 0 r---- LC_TIME 00007f47dd19e000 4 4 0 r---- LC_MONETARY 00007f47dd19f000 4 4 0 r---- SYS_LC_MESSAGES 00007f47dd1a0000 4 4 0 r---- LC_PAPER 00007f47dd1a1000 8 4 4 rw--- [ anon ] 00007f47dd1a3000 4 4 0 r---- LC_NAME 00007f47dd1a4000 4 4 0 r---- LC_ADDRESS 00007f47dd1a5000 4 4 0 r---- LC_TELEPHONE 00007f47dd1a6000 4 4 0 r---- LC_MEASUREMENT 00007f47dd1a7000 28 28 0 r--s- gconv-modules.cache 00007f47dd1ae000 4 4 0 r---- LC_IDENTIFICATION 00007f47dd1af000 8 8 8 rw--- [ anon ] 00007f47dd1b1000 4 4 4 r---- ld-2.28.so 00007f47dd1b2000 8 8 8 rw--- ld-2.28.so 00007fff6435e000 132 12 12 rw--- [ stack ] 00007fff6438d000 16 0 0 r---- [ anon ] 00007fff64391000 8 4 0 r-x-- [ anon ] ffffffffff600000 4 0 0 r-x-- [ anon ] ---------------- ------- ------- ------- total kB 7532 1912 104 herong$ sudo cat /proc/649848/maps 56392fc85000-56392fc8c000 r-xp 00000000 fd:00 63570 /usr/bin/sleep 56392fe8c000-56392fe8d000 r--p 00007000 fd:00 63570 /usr/bin/sleep 56392fe8d000-56392fe8e000 rw-p 00008000 fd:00 63570 /usr/bin/sleep 563931dd7000-563931df8000 rw-p 00000000 00:00 0 [heap] 7f47dc913000-7f47dcbc0000 r--p 00000000 fd:00 33630723 /usr/lib/locale/zh_CN.utf8/LC_COLLATE 7f47dcbc0000-7f47dcd7c000 r-xp 00000000 fd:00 75501124 /usr/lib64/libc-2.28.so 7f47dcd7c000-7f47dcf7b000 ---p 001bc000 fd:00 75501124 /usr/lib64/libc-2.28.so 7f47dcf7b000-7f47dcf7f000 r--p 001bb000 fd:00 75501124 /usr/lib64/libc-2.28.so 7f47dcf7f000-7f47dcf81000 rw-p 001bf000 fd:00 75501124 /usr/lib64/libc-2.28.so 7f47dcf81000-7f47dcf85000 rw-p 00000000 00:00 0 7f47dcf85000-7f47dcfb1000 r-xp 00000000 fd:00 76867831 /usr/lib64/ld-2.28.so 7f47dd149000-7f47dd19c000 r--p 00000000 fd:00 33557602 /usr/lib/locale/zh_CN.utf8/LC_CTYPE 7f47dd19c000-7f47dd19d000 r--p 00000000 fd:00 33630731 /usr/lib/locale/zh_CN.utf8/LC_NUMERIC 7f47dd19d000-7f47dd19e000 r--p 00000000 fd:00 33630727 /usr/lib/locale/zh_CN.utf8/LC_TIME 7f47dd19e000-7f47dd19f000 r--p 00000000 fd:00 33630725 /usr/lib/locale/zh_CN.utf8/LC_MONETARY 7f47dd19f000-7f47dd1a0000 r--p 00000000 fd:00 42190048 /usr/lib/locale/zh_CN.utf8/LC_MESSA... 7f47dd1a0000-7f47dd1a1000 r--p 00000000 fd:00 33630732 /usr/lib/locale/zh_CN.utf8/LC_PAPER 7f47dd1a1000-7f47dd1a3000 rw-p 00000000 00:00 0 7f47dd1a3000-7f47dd1a4000 r--p 00000000 fd:00 33630730 /usr/lib/locale/zh_CN.utf8/LC_NAME 7f47dd1a4000-7f47dd1a5000 r--p 00000000 fd:00 33630722 /usr/lib/locale/zh_CN.utf8/LC_ADDRESS 7f47dd1a5000-7f47dd1a6000 r--p 00000000 fd:00 33630726 /usr/lib/locale/zh_CN.utf8/LC_TELEPHONE 7f47dd1a6000-7f47dd1a7000 r--p 00000000 fd:00 33630729 /usr/lib/locale/zh_CN.utf8/LC_MEASU... 7f47dd1a7000-7f47dd1ae000 r--s 00000000 fd:00 109056718 /usr/lib64/gconv/gconv-modules.cache 7f47dd1ae000-7f47dd1af000 r--p 00000000 fd:00 33630724 /usr/lib/locale/zh_CN.utf8/LC_IDENT... 7f47dd1af000-7f47dd1b1000 rw-p 00000000 00:00 0 7f47dd1b1000-7f47dd1b2000 r--p 0002c000 fd:00 76867831 /usr/lib64/ld-2.28.so 7f47dd1b2000-7f47dd1b4000 rw-p 0002d000 fd:00 76867831 /usr/lib64/ld-2.28.so 7fff6435e000-7fff6437f000 rw-p 00000000 00:00 0 [stack] 7fff6438d000-7fff64391000 r--p 00000000 00:00 0 [vvar] 7fff64391000-7fff64393000 r-xp 00000000 00:00 0 [vdso] ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]
The output confirms that the "pmap" command is using the "/proc/{id}/maps" pseudo file to generate report.
Table of Contents
Cockpit - Web Portal for Administrator
Layers of Memory and Access Speed
List CPU Caches and Their Sizes
Virtual Memory vs. Physical Memory
Buffer Memory and Cache Memory
Verify Cache Memory with "cp" Command
Virtual Memory Mapping and Page Table
"ps -o rss,drs,trs,vsz,sz" - Process Status Options
smem - Process Memory Usage Report
►/proc/{id}/maps - Process Memory Map
/proc/{id}/smaps - Process Memory Map Details
SELinux - Security-Enhanced Linux
SSH Protocol and ssh/scp Commands
Software Package Manager on CentOS - DNF and YUM
vsftpd - Very Secure FTP Daemon