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 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. -- 2.1.4 -- 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
