proc_pid_smaps(5)

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 would-be-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 counter-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).

    The "VmFlags" line (available since Linux 3.8) represents the kernel flags associated with the virtual memory area, encoded using the following two-letter codes:

        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 | - | non-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 | - | soft-dirty flag (since Linux 3.13)
        mm | - | mixed map area
        hg | - | huge page advise flag
        nh | - | no-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)

    The /proc/pid/smaps file is present only if the CONFIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

SEE ALSO
proc(5)