proc_buddyinfo(5)             File Formats Manual            proc_buddyinfo(5)

NAME
       /proc/buddyinfo - memory fragmentation

DESCRIPTION
       /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:

                  (2^order) * PAGE_SIZE

              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.

              For example on an x86-64 system:
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

              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 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.

              If the memory is heavily fragmented, the counters for higher
              order chunks will be zero and allocation of large contiguous
              areas will fail.

              Further information about the zones can be found in
              /proc/zoneinfo.

SEE ALSO
       proc(5)

Linux man-pages 6.9.1             2024-05-02                 proc_buddyinfo(5)