On 09/27/2014 07:35 PM, Elie De Brauwer wrote: > This patch adds a short description about the contents of > /proc/buddyinfo and how this file can be used to assist > in checking for memory fragmentation issues. Elie, Thanks for the background note (your previous mail). I've applied this patch; thanks for sending it. Cheers, Michael > > Signed-off-by: Elie De Brauwer <eliedebrauwer@xxxxxxxxx> > --- > man5/proc.5 | 39 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 39 insertions(+) > > diff --git a/man5/proc.5 b/man5/proc.5 > index 337f6b6..777611a 100644 > --- a/man5/proc.5 > +++ b/man5/proc.5 > @@ -1825,6 +1825,45 @@ Advanced power management version and battery information when > .B CONFIG_APM > is defined at kernel compilation time. > .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: > +.IR "(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 a x86_64 system: > +.in +4n > +.nf > +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 > +.fi > +.in > + > +In this example there is one node containing three zones and there > +are 11 different chunk sizes. > +If the page size is 4 kilobyte, then the first zone called > +.I DMA > +(on x86 the first 16 megabyte of memory) has 1 chunk of 4 kilobyte > +(order 0) available and has 3 chunks of 4 megabyte (order 10) available. > + > +If the memory is heavily fragmentated, 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 > +.IR /proc/zoneinfo . > +.TP > .I /proc/bus > Contains subdirectories for installed busses. > .TP > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
