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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-15 19:41:07 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-15 19:41:07 +0000
commit3af6d22bb3850ab2bac67287e3a3d3b0e32868e5 (patch)
tree3ee7a3ec64525911fa865bb984c86d997d855527 /man5/proc_buddyinfo.5
parentAdding debian version 6.05.01-1. (diff)
downloadmanpages-3af6d22bb3850ab2bac67287e3a3d3b0e32868e5.tar.xz
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Merging upstream version 6.7.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.\" 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_buddyinfo 5 2023-08-15 "Linux man-pages 6.7"
+.SH NAME
+/proc/buddyinfo \- memory fragmentation
+.SH DESCRIPTION
+.TP
+.I /proc/buddyinfo
+This file contains information which is used for diagnosing memory
+fragmentation issues.
+Each line starts with the identification of the node and the name
+of the zone which together identify a memory region.
+This is then
+followed by the count of available chunks of a certain order in
+which these zones are split.
+The size in bytes of a certain order is given by the formula:
+.IP
+.in +4n
+.EX
+(2\[ha]order)\ *\ PAGE_SIZE
+.EE
+.in
+.IP
+The binary buddy allocator algorithm inside the kernel will split
+one chunk into two chunks of a smaller order (thus with half the
+size) or combine two contiguous chunks into one larger chunk of
+a higher order (thus with double the size) to satisfy allocation
+requests and to counter memory fragmentation.
+The order matches the column number, when starting to count at zero.
+.IP
+For example on an x86-64 system:
+.RS -12
+.EX
+Node 0, zone DMA 1 1 1 0 2 1 1 0 1 1 3
+Node 0, zone DMA32 65 47 4 81 52 28 13 10 5 1 404
+Node 0, zone Normal 216 55 189 101 84 38 37 27 5 3 587
+.EE
+.RE
+.IP
+In this example, there is one node containing three zones and there
+are 11 different chunk sizes.
+If the page size is 4 kilobytes, then the first zone called
+.I DMA
+(on x86 the first 16 megabyte of memory) has 1 chunk of 4 kilobytes
+(order 0) available and has 3 chunks of 4 megabytes (order 10) available.
+.IP
+If the memory is heavily fragmented, the counters for higher
+order chunks will be zero and allocation of large contiguous areas
+will fail.
+.IP
+Further information about the zones can be found in
+.IR /proc/zoneinfo .
+.SH SEE ALSO
+.BR proc (5)