The patch titled
migration: only migrate_prep() once per move_pages()
has been added to the -mm tree. Its filename is
migration-only-migrate_prep-once-per-move_pages.patch
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------------------------------------------------------
Subject: migration: only migrate_prep() once per move_pages()
From: Brice Goglin <Brice.Goglin@xxxxxxxxxxxx>
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@xxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
Cc: Hugh Dickins <hugh@xxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff -puN mm/migrate.c~migration-only-migrate_prep-once-per-move_pages mm/migrate.c
--- a/mm/migrate.c~migration-only-migrate_prep-once-per-move_pages
+++ a/mm/migrate.c
@@ -820,7 +820,6 @@ static int do_move_page_to_node_array(st
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_struc
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
_
Patches currently in -mm which might be from Brice.Goglin@xxxxxxxxxxxx are
migration-only-migrate_prep-once-per-move_pages.patch
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