Commit 35282a2d authored Jun 16, 2009 by Brice Goglin Committed by Linus Torvalds Jun 16, 2009

migration: only migrate_prep() once per move_pages()



migrate_prep() is fairly expensive (72us on 16-core barcelona 1.9GHz).
Commit 3140a227 improved move_pages()
throughput by breaking it into chunks, but it also made migrate_prep() be
called once per chunk (every 128pages or so) instead of once per
move_pages().

This patch reverts to calling migrate_prep() only once per chunk as we did
before 2.6.29.  It is also a followup to commit
0aedadf9 ("mm: move migrate_prep out from
under mmap_sem").

This improves migration throughput on the above machine from 600MB/s to
750MB/s.

Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Rik van Riel <riel@redhat.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 7f33d49a

mm/migrate.c

+3 −1

Original line number	Original line	Diff line number	Diff line
	@@ -820,7 +820,6 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
	struct page_to_node *pp;		struct page_to_node *pp;
	LIST_HEAD(pagelist);		LIST_HEAD(pagelist);

	migrate_prep();
	down_read(&mm->mmap_sem);		down_read(&mm->mmap_sem);

	/*		/*
	@@ -907,6 +906,9 @@ static int do_pages_move(struct mm_struct mm, struct task_struct task,
	pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);		pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
	if (!pm)		if (!pm)
	goto out;		goto out;

			migrate_prep();

	/*		/*
	* Store a chunk of page_to_node array in a page,		* Store a chunk of page_to_node array in a page,
	* but keep the last one as a marker		* but keep the last one as a marker