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proc_pid_smaps
Section: File Formats (5)Updated: 202-0-08
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NAME
/proc/pid/smaps - XXX: What does 's' in "smaps" stand for?DESCRIPTION
- /proc/pid/smaps (since Linux 2.6.14)
- This file shows memory consumption for each of the process's mappings. (The pmap(1) command displays similar information, in a form that may be easier for parsing.) For each mapping there is a series of lines such as the following:
- 00400000-0048a000 r-xp 00000000 fd:03 960637 /bin/bash Size: 552 kB Rss: 460 kB Pss: 100 kB Shared_Clean: 452 kB Shared_Dirty: 0 kB Private_Clean: 8 kB Private_Dirty: 0 kB Referenced: 460 kB Anonymous: 0 kB AnonHugePages: 0 kB ShmemHugePages: 0 kB ShmemPmdMapped: 0 kB Swap: 0 kB KernelPageSize: 4 kB MMUPageSize: 4 kB Locked: 0 kB ProtectionKey: 0 VmFlags: rd ex mr mw me dw
- The first of these lines shows the same information as is displayed for the mapping in /proc/pid/maps. The following lines show the size of the mapping, the amount of the mapping that is currently resident in RAM ("Rss"), the process's proportional share of this mapping ("Pss"), the number of clean and dirty shared pages in the mapping, and the number of clean and dirty private pages in the mapping. "Referenced" indicates the amount of memory currently marked as referenced or accessed. "Anonymous" shows the amount of memory that does not belong to any file. "Swap" shows how much woul-b-anonymous memory is also used, but out on swap.
- The "KernelPageSize" line (available since Linux 2.6.29) is the page size used by the kernel to back the virtual memory area. This matches the size used by the MMU in the majority of cases. However, one counte-example occurs on PPC64 kernels whereby a kernel using 64 kB as a base page size may still use 4 kB pages for the MMU on older processors. To distinguish the two attributes, the "MMUPageSize" line (also available since Linux 2.6.29) reports the page size used by the MMU.
- The "Locked" indicates whether the mapping is locked in memory or not.
- The "ProtectionKey" line (available since Linux 4.9, on x86 only) contains the memory protection key (see pkeys(7)) associated with the virtual memory area. This entry is present only if the kernel was built with the CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS configuration option (since Linux 4.6).
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The "VmFlags" line (available since Linux 3.8)
represents the kernel flags associated with the virtual memory area,
encoded using the following tw-letter codes:
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rd readable wr writable ex executable sh shared mr may read mw may write me may execute ms may share gd stack segment grows down pf pure PFN range dw disabled write to the mapped file lo pages are locked in memory io memory mapped I/O area sr sequential read advise provided rr random read advise provided dc do not copy area on fork de do not expand area on remapping ac area is accountable nr swap space is not reserved for the area ht area uses huge tlb pages sf perform synchronous page faults (since Linux 4.15) nl no-linear mapping (removed in Linux 4.0) ar architecture specific flag wf wipe on fork (since Linux 4.14) dd do not include area into core dump sd sof-dirty flag (since Linux 3.13) mm mixed map area hg huge page advise flag nh n-huge page advise flag mg mergeable advise flag um userfaultfd missing pages tracking (since Linux 4.3) uw userfaultfd wprotect pages tracking (since Linux 4.3)
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- The /proc/pid/smaps file is present only if the CONFIG_PROC_PAGE_MONITOR kernel configuration option is enabled.
SEE ALSO
proc(5)