Re: [PATCH -mm V3] do_migrate_pages() calls migrate_to_node() evenif task is already on a correct node

From: Rik van Riel
Date: Thu Apr 26 2012 - 14:15:46 EST


On 04/26/2012 02:11 PM, Larry Woodman wrote:

This patch changes do_migrate_pages() to only preserve the relative
layout inside the
program if the number of NUMA nodes in the source and destination mask
are the
same. If the number is different, we do a much more efficient migration
by not touching
memory that is in an allowed node.

This preserves the old behaviour for programs that want it, while
allowing a userspace
NUMA placement tool to use the new, faster migration. This improves
performance in
our tests by up to a factor of 7.

Signed-off-by: Larry Woodman<lwoodman@xxxxxxxxxx>

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

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