On 01/22/2015 08:21 PM, Elie De Brauwer wrote: > Since 2.6.36 [1] CONFIG_COMPACTION is supported in Linux (for a > detailed explanation see [2]). But in essence the contents of /proc/buddyinfo > shows how much contiguous areas of a certain size are available. These > numbers are not actually up to date as the Linux kernel will implicitely > trigger compaction (+- defragmentation) when an allocation is done. > This makes it difficult since you can't predict upfront whether or not a > large allocation will succeed or not. > By using /proc/sys/vm/compact_memory you can explicitely trigger compaction > to occur and /proc/buddyinfo will give a more realistic view on the > available memory in contiguous areas. > > This patch updates proc.5 to explain the usage of this file and is > inspired upon Documentation/systcl/vm.txt [3] > > [1] http://kernelnewbies.org/Linux_2_6_35#head-9cb0a1275559d40296da42efb7977896ac9edab7 > [2] http://lwn.net/Articles/368869/ > [3] http://lxr.free-electrons.com/source/Documentation/sysctl/vm.txt#L100 Thanks, Elie. Applied. Cheers, Michael > Signed-off-by: Elie De Brauwer <eliedebrauwer@xxxxxxxxx> > --- > man5/proc.5 | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/man5/proc.5 b/man5/proc.5 > index 860eb66..5bff2a0 100644 > --- a/man5/proc.5 > +++ b/man5/proc.5 > @@ -3943,6 +3943,15 @@ On some systems, it is not present. > This directory contains files for memory management tuning, buffer and > cache management. > .TP > +.IR /proc/sys/vm/compact_memory " (since Linux 2.6.35)" > +When 1 is written to this file, all zones are compacted such that free > +memory is available in contiguous blocks where possible. > +The effect of this action can be seen by examining > +.IR /proc/buddyinfo . > +.IP > +Only present if the kernel was configured with > +.BR CONFIG_COMPACTION . > +.TP > .IR /proc/sys/vm/drop_caches " (since Linux 2.6.16)" > Writing to this file causes the kernel to drop clean caches, dentries, and > inodes from memory, causing that memory to become free. > -- 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
