From: Brice Goglin <Brice.Goglin@ens-lyon.org>
Date: Tue, 16 Jun 2009 22:32:43 +0000 (-0700)
Subject: migration: only migrate_prep() once per move_pages()
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=35282a2de4e5e4e173ab61aa9d7015886021a821;p=linux-beck.git

migration: only migrate_prep() once per move_pages()

migrate_prep() is fairly expensive (72us on 16-core barcelona 1.9GHz).
Commit 3140a2273009c01c27d316f35ab76a37e105fdd8 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
0aedadf91a70a11c4a3e7c7d99b21e5528af8d5d ("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>
---

diff --git a/mm/migrate.c b/mm/migrate.c
index 5a24923e7fd7..939888f9ddab 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -820,7 +820,6 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
 	struct page_to_node *pp;
 	LIST_HEAD(pagelist);
 
-	migrate_prep();
 	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);
 	if (!pm)
 		goto out;
+
+	migrate_prep();
+
 	/*
 	 * Store a chunk of page_to_node array in a page,
 	 * but keep the last one as a marker