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famzah/The virtual and real memory usage of mmap()'ed memory Secret

Created December 4, 2020 10:04
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The virtual and real memory usage of mmap()'ed memory
# stat doesn't give us the real usage, only the virtual
famzah@vbox64:~$ sudo stat -L /proc/9256/map_files/7f052ea9b000-7f05aba9b000
File: /proc/9256/map_files/7f052ea9b000-7f05aba9b000
Size: 2097152000 Blocks: 2048000 IO Block: 4096 regular file
Device: 5h/5d Inode: 733825 Links: 0
Access: (0777/-rwxrwxrwx) Uid: ( 1000/ famzah) Gid: ( 1000/ famzah)
# VSS (virtual memory size)
famzah@vbox64:~$ sudo du --apparent-size -BM -D /proc/9256/map_files/7f052ea9b000-7f05aba9b000
2000M /proc/9256/map_files/7f052ea9b000-7f05aba9b000
# RSS (resident set size, or simply "the real usage")
famzah@vbox64:~$ sudo du -BM -D /proc/9256/map_files/7f052ea9b000-7f05aba9b000
1000M /proc/9256/map_files/7f052ea9b000-7f05aba9b000
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