diff options
Diffstat (limited to 'man5/proc_meminfo.5')
| -rw-r--r-- | man5/proc_meminfo.5 | 327 |
1 files changed, 327 insertions, 0 deletions
diff --git a/man5/proc_meminfo.5 b/man5/proc_meminfo.5 new file mode 100644 index 0000000..7a2e70e --- /dev/null +++ b/man5/proc_meminfo.5 @@ -0,0 +1,327 @@ +.\" Copyright (C) 1994, 1995, Daniel Quinlan <quinlan@yggdrasil.com> +.\" Copyright (C) 2002-2008, 2017, Michael Kerrisk <mtk.manpages@gmail.com> +.\" Copyright (C) 2023, Alejandro Colomar <alx@kernel.org> +.\" +.\" SPDX-License-Identifier: GPL-3.0-or-later +.\" +.TH proc_meminfo 5 2023-08-15 "Linux man-pages 6.7" +.SH NAME +/proc/meminfo \- memory usage +.SH DESCRIPTION +.TP +.I /proc/meminfo +This file reports statistics about memory usage on the system. +It is used by +.BR free (1) +to report the amount of free and used memory (both physical and swap) +on the system as well as the shared memory and buffers used by the +kernel. +Each line of the file consists of a parameter name, followed by a colon, +the value of the parameter, and an option unit of measurement (e.g., "kB"). +The list below describes the parameter names and +the format specifier required to read the field value. +Except as noted below, +all of the fields have been present since at least Linux 2.6.0. +Some fields are displayed only if the kernel was configured +with various options; those dependencies are noted in the list. +.RS +.TP +.IR MemTotal " %lu" +Total usable RAM (i.e., physical RAM minus a few reserved +bits and the kernel binary code). +.TP +.IR MemFree " %lu" +The sum of +.IR LowFree + HighFree . +.TP +.IR MemAvailable " %lu (since Linux 3.14)" +An estimate of how much memory is available for starting new +applications, without swapping. +.TP +.IR Buffers " %lu" +Relatively temporary storage for raw disk blocks that +shouldn't get tremendously large (20 MB or so). +.TP +.IR Cached " %lu" +In-memory cache for files read from the disk (the page cache). +Doesn't include +.IR SwapCached . +.TP +.IR SwapCached " %lu" +Memory that once was swapped out, is swapped back in but +still also is in the swap file. +(If memory pressure is high, these pages +don't need to be swapped out again because they are already +in the swap file. +This saves I/O.) +.TP +.IR Active " %lu" +Memory that has been used more recently and usually not +reclaimed unless absolutely necessary. +.TP +.IR Inactive " %lu" +Memory which has been less recently used. +It is more eligible to be reclaimed for other purposes. +.TP +.IR Active(anon) " %lu (since Linux 2.6.28)" +[To be documented.] +.TP +.IR Inactive(anon) " %lu (since Linux 2.6.28)" +[To be documented.] +.TP +.IR Active(file) " %lu (since Linux 2.6.28)" +[To be documented.] +.TP +.IR Inactive(file) " %lu (since Linux 2.6.28)" +[To be documented.] +.TP +.IR Unevictable " %lu (since Linux 2.6.28)" +(From Linux 2.6.28 to Linux 2.6.30, +\fBCONFIG_UNEVICTABLE_LRU\fP was required.) +[To be documented.] +.TP +.IR Mlocked " %lu (since Linux 2.6.28)" +(From Linux 2.6.28 to Linux 2.6.30, +\fBCONFIG_UNEVICTABLE_LRU\fP was required.) +[To be documented.] +.TP +.IR HighTotal " %lu" +(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.) +Total amount of highmem. +Highmem is all memory above \[ti]860 MB of physical memory. +Highmem areas are for use by user-space programs, +or for the page cache. +The kernel must use tricks to access +this memory, making it slower to access than lowmem. +.TP +.IR HighFree " %lu" +(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.) +Amount of free highmem. +.TP +.IR LowTotal " %lu" +(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.) +Total amount of lowmem. +Lowmem is memory which can be used for everything that +highmem can be used for, but it is also available for the +kernel's use for its own data structures. +Among many other things, +it is where everything from +.I Slab +is allocated. +Bad things happen when you're out of lowmem. +.TP +.IR LowFree " %lu" +(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.) +Amount of free lowmem. +.TP +.IR MmapCopy " %lu (since Linux 2.6.29)" +.RB ( CONFIG_MMU +is required.) +[To be documented.] +.TP +.IR SwapTotal " %lu" +Total amount of swap space available. +.TP +.IR SwapFree " %lu" +Amount of swap space that is currently unused. +.TP +.IR Dirty " %lu" +Memory which is waiting to get written back to the disk. +.TP +.IR Writeback " %lu" +Memory which is actively being written back to the disk. +.TP +.IR AnonPages " %lu (since Linux 2.6.18)" +Non-file backed pages mapped into user-space page tables. +.TP +.IR Mapped " %lu" +Files which have been mapped into memory (with +.BR mmap (2)), +such as libraries. +.TP +.IR Shmem " %lu (since Linux 2.6.32)" +Amount of memory consumed in +.BR tmpfs (5) +filesystems. +.TP +.IR KReclaimable " %lu (since Linux 4.20)" +Kernel allocations that the kernel will attempt to reclaim +under memory pressure. +Includes +.I SReclaimable +(below), and other direct allocations with a shrinker. +.TP +.IR Slab " %lu" +In-kernel data structures cache. +(See +.BR slabinfo (5).) +.TP +.IR SReclaimable " %lu (since Linux 2.6.19)" +Part of +.IR Slab , +that might be reclaimed, such as caches. +.TP +.IR SUnreclaim " %lu (since Linux 2.6.19)" +Part of +.IR Slab , +that cannot be reclaimed on memory pressure. +.TP +.IR KernelStack " %lu (since Linux 2.6.32)" +Amount of memory allocated to kernel stacks. +.TP +.IR PageTables " %lu (since Linux 2.6.18)" +Amount of memory dedicated to the lowest level of page tables. +.TP +.IR Quicklists " %lu (since Linux 2.6.27)" +(\fBCONFIG_QUICKLIST\fP is required.) +[To be documented.] +.TP +.IR NFS_Unstable " %lu (since Linux 2.6.18)" +NFS pages sent to the server, but not yet committed to stable storage. +.TP +.IR Bounce " %lu (since Linux 2.6.18)" +Memory used for block device "bounce buffers". +.TP +.IR WritebackTmp " %lu (since Linux 2.6.26)" +Memory used by FUSE for temporary writeback buffers. +.TP +.IR CommitLimit " %lu (since Linux 2.6.10)" +This is the total amount of memory currently available to +be allocated on the system, expressed in kilobytes. +This limit is adhered to +only if strict overcommit accounting is enabled (mode 2 in +.IR /proc/sys/vm/overcommit_memory ). +The limit is calculated according to the formula described under +.IR /proc/sys/vm/overcommit_memory . +For further details, see the kernel source file +.IR Documentation/vm/overcommit\-accounting.rst . +.TP +.IR Committed_AS " %lu" +The amount of memory presently allocated on the system. +The committed memory is a sum of all of the memory which +has been allocated by processes, even if it has not been +"used" by them as of yet. +A process which allocates 1 GB of memory (using +.BR malloc (3) +or similar), but touches only 300 MB of that memory will show up +as using only 300 MB of memory even if it has the address space +allocated for the entire 1 GB. +.IP +This 1 GB is memory which has been "committed" to by the VM +and can be used at any time by the allocating application. +With strict overcommit enabled on the system (mode 2 in +.IR /proc/sys/vm/overcommit_memory ), +allocations which would exceed the +.I CommitLimit +will not be permitted. +This is useful if one needs to guarantee that processes will not +fail due to lack of memory once that memory has been successfully allocated. +.TP +.IR VmallocTotal " %lu" +Total size of vmalloc memory area. +.TP +.IR VmallocUsed " %lu" +Amount of vmalloc area which is used. +Since Linux 4.4, +.\" commit a5ad88ce8c7fae7ddc72ee49a11a75aa837788e0 +this field is no longer calculated, and is hard coded as 0. +See +.IR /proc/vmallocinfo . +.TP +.IR VmallocChunk " %lu" +Largest contiguous block of vmalloc area which is free. +Since Linux 4.4, +.\" commit a5ad88ce8c7fae7ddc72ee49a11a75aa837788e0 +this field is no longer calculated and is hard coded as 0. +See +.IR /proc/vmallocinfo . +.TP +.IR HardwareCorrupted " %lu (since Linux 2.6.32)" +(\fBCONFIG_MEMORY_FAILURE\fP is required.) +[To be documented.] +.TP +.IR LazyFree " %lu (since Linux 4.12)" +Shows the amount of memory marked by +.BR madvise (2) +.BR MADV_FREE . +.TP +.IR AnonHugePages " %lu (since Linux 2.6.38)" +(\fBCONFIG_TRANSPARENT_HUGEPAGE\fP is required.) +Non-file backed huge pages mapped into user-space page tables. +.TP +.IR ShmemHugePages " %lu (since Linux 4.8)" +(\fBCONFIG_TRANSPARENT_HUGEPAGE\fP is required.) +Memory used by shared memory (shmem) and +.BR tmpfs (5) +allocated with huge pages. +.TP +.IR ShmemPmdMapped " %lu (since Linux 4.8)" +(\fBCONFIG_TRANSPARENT_HUGEPAGE\fP is required.) +Shared memory mapped into user space with huge pages. +.TP +.IR CmaTotal " %lu (since Linux 3.1)" +Total CMA (Contiguous Memory Allocator) pages. +(\fBCONFIG_CMA\fP is required.) +.TP +.IR CmaFree " %lu (since Linux 3.1)" +Free CMA (Contiguous Memory Allocator) pages. +(\fBCONFIG_CMA\fP is required.) +.TP +.IR HugePages_Total " %lu" +(\fBCONFIG_HUGETLB_PAGE\fP is required.) +The size of the pool of huge pages. +.TP +.IR HugePages_Free " %lu" +(\fBCONFIG_HUGETLB_PAGE\fP is required.) +The number of huge pages in the pool that are not yet allocated. +.TP +.IR HugePages_Rsvd " %lu (since Linux 2.6.17)" +(\fBCONFIG_HUGETLB_PAGE\fP is required.) +This is the number of huge pages for +which a commitment to allocate from the pool has been made, +but no allocation has yet been made. +These reserved huge pages +guarantee that an application will be able to allocate a +huge page from the pool of huge pages at fault time. +.TP +.IR HugePages_Surp " %lu (since Linux 2.6.24)" +(\fBCONFIG_HUGETLB_PAGE\fP is required.) +This is the number of huge pages in +the pool above the value in +.IR /proc/sys/vm/nr_hugepages . +The maximum number of surplus huge pages is controlled by +.IR /proc/sys/vm/nr_overcommit_hugepages . +.TP +.IR Hugepagesize " %lu" +(\fBCONFIG_HUGETLB_PAGE\fP is required.) +The size of huge pages. +.TP +.IR DirectMap4k " %lu (since Linux 2.6.27)" +Number of bytes of RAM linearly mapped by kernel in 4 kB pages. +(x86.) +.TP +.IR DirectMap4M " %lu (since Linux 2.6.27)" +Number of bytes of RAM linearly mapped by kernel in 4 MB pages. +(x86 with +.B CONFIG_X86_64 +or +.B CONFIG_X86_PAE +enabled.) +.TP +.IR DirectMap2M " %lu (since Linux 2.6.27)" +Number of bytes of RAM linearly mapped by kernel in 2 MB pages. +(x86 with neither +.B CONFIG_X86_64 +nor +.B CONFIG_X86_PAE +enabled.) +.TP +.IR DirectMap1G " %lu (since Linux 2.6.27)" +(x86 with +.B CONFIG_X86_64 +and +.B CONFIG_X86_DIRECT_GBPAGES +enabled.) +.RE +.SH SEE ALSO +.BR proc (5) |