From 6fe6b2d6dabf392aceb3ad3a5e859b46a04465c6 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Mon, 7 Oct 2013 11:29:08 +0100 Subject: sched/numa: Do not migrate memory immediately after switching node The load balancer can move tasks between nodes and does not take NUMA locality into account. With automatic NUMA balancing this may result in the tasks working set being migrated to the new node. However, as the fault buffer will still store faults from the old node the schduler may decide to reset the preferred node and migrate the task back resulting in more migrations. The ideal would be that the scheduler did not migrate tasks with a heavy memory footprint but this may result nodes being overloaded. We could also discard the fault information on task migration but this would still cause all the tasks working set to be migrated. This patch simply avoids migrating the memory for a short time after a task is migrated. Signed-off-by: Rik van Riel Signed-off-by: Mel Gorman Cc: Andrea Arcangeli Cc: Johannes Weiner Cc: Srikar Dronamraju Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1381141781-10992-31-git-send-email-mgorman@suse.de Signed-off-by: Ingo Molnar --- mm/mempolicy.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'mm/mempolicy.c') diff --git a/mm/mempolicy.c b/mm/mempolicy.c index aff1f1ed3dc5..196d8da2b657 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2378,6 +2378,18 @@ int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long last_nidpid = page_nidpid_xchg_last(page, this_nidpid); if (!nidpid_pid_unset(last_nidpid) && nidpid_to_nid(last_nidpid) != polnid) goto out; + +#ifdef CONFIG_NUMA_BALANCING + /* + * If the scheduler has just moved us away from our + * preferred node, do not bother migrating pages yet. + * This way a short and temporary process migration will + * not cause excessive memory migration. + */ + if (polnid != current->numa_preferred_nid && + !current->numa_migrate_seq) + goto out; +#endif } if (curnid != polnid) -- cgit v1.2.3