On 10/07/15 07:27, mathog wrote: > Well, that seems to be it, but not quite with the same symptoms you > observed. khugepaged never showed up, and "perf top" never revealed > _spin_lock_irqsave. Instead this is what "perf top" shows in my tests:
So this sounds look like the same symptoms as reported here too: http://structureddata.org/2012/06/18/linux-6-transparent-huge-pages-and-hadoop-workloads/ There they note that: # Looking at the functions listed in the Flame Graph (below) # it looked like the issue was related to virtual memory and # the Linux source shows many of these functions are in # linux/mm/compaction.c. which is indeed where compation_alloc() lives. The kernel describes that function as: /* * This is a migrate-callback that "allocates" freepages by taking pages * from the isolated freelists in the block we are migrating to. */ /* * Isolate free pages if necessary, and if we are not aborting due to * contention. */ Introduced by this commit: commit 748446bb6b5a9390b546af38ec899c868a9dbcf0 Author: Mel Gorman <[email protected]> Date: Mon May 24 14:32:27 2010 -0700 mm: compaction: memory compaction core This patch is the core of a mechanism which compacts memory in a zone by relocating movable pages towards the end of the zone. A single compaction run involves a migration scanner and a free scanner. Both scanners operate on pageblock-sized areas in the zone. The migration scanner starts at the bottom of the zone and searches for all movable pages within each area, isolating them onto a private list called migratelist. The free scanner starts at the top of the zone and searches for suitable areas and consumes the free pages within making them available for the migration scanner. The pages isolated for migration are then migrated to the newly isolated free pages. [[email protected]: Fix unsafe optimisation] [[email protected]: do not schedule work on other CPUs for compaction] Signed-off-by: Mel Gorman <[email protected]> Acked-by: Rik van Riel <[email protected]> Reviewed-by: Minchan Kim <[email protected]> Cc: KOSAKI Motohiro <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: KAMEZAWA Hiroyuki <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> All the best, Chris -- Christopher Samuel Senior Systems Administrator VLSCI - Victorian Life Sciences Computation Initiative Email: [email protected] Phone: +61 (0)3 903 55545 http://www.vlsci.org.au/ http://twitter.com/vlsci _______________________________________________ Beowulf mailing list, [email protected] sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
