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mm: fold page->_last_nid into page->flags where possible

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page->_last_nid fits into page->flags on 64-bit.  The unlikely 32-bit
NUMA configuration with NUMA Balancing will still need an extra page
field.  As Peter notes "Completely dropping 32bit support for
CONFIG_NUMA_BALANCING would simplify things, but it would also remove
the warning if we grow enough 64bit only page-flags to push the last-cpu
out."

[mgorman@suse.de: minor modifications]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Simon Jeons <simon.jeons@gmail.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Peter Zijlstra 2013-02-22 16:34:32 -08:00 • committed by Linus Torvalds
parent bbeae5b05e
commit 75980e97da
4 changed files with 62 additions and 10 deletions
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33
include/linux/page-flags-layout.h
View file

@ -32,15 +32,16 @@
/*
* page->flags layout:
*
* There are three possibilities for how page->flags get
* laid out. The first is for the normal case, without
* sparsemem. The second is for sparsemem when there is
* plenty of space for node and section. The last is when
* we have run out of space and have to fall back to an
* alternate (slower) way of determining the node.
* There are five possibilities for how page->flags get laid out. The first
* pair is for the normal case without sparsemem. The second pair is for
* sparsemem when there is plenty of space for node and section information.
* The last is when there is insufficient space in page->flags and a separate
* lookup is necessary.
*
* No sparsemem or sparsemem vmemmap: | NODE | ZONE | ... | FLAGS |
* classic sparse with space for node:| SECTION | NODE | ZONE | ... | FLAGS |
* No sparsemem or sparsemem vmemmap: | NODE | ZONE | ... | FLAGS |
* " plus space for last_nid: | NODE | ZONE | LAST_NID ... | FLAGS |
* classic sparse with space for node:| SECTION | NODE | ZONE | ... | FLAGS |
* " plus space for last_nid: | SECTION | NODE | ZONE | LAST_NID ... | FLAGS |
* classic sparse no space for node: | SECTION | ZONE | ... | FLAGS |
*/
#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
@ -60,6 +61,18 @@
#define NODES_WIDTH 0
#endif
#ifdef CONFIG_NUMA_BALANCING
#define LAST_NID_SHIFT NODES_SHIFT
#else
#define LAST_NID_SHIFT 0
#endif
#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_NID_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
#define LAST_NID_WIDTH LAST_NID_SHIFT
#else
#define LAST_NID_WIDTH 0
#endif
/*
* We are going to use the flags for the page to node mapping if its in
* there. This includes the case where there is no node, so it is implicit.
@ -68,4 +81,8 @@
#define NODE_NOT_IN_PAGE_FLAGS
#endif
#if defined(CONFIG_NUMA_BALANCING) && LAST_NID_WIDTH == 0
#define LAST_NID_NOT_IN_PAGE_FLAGS
#endif
#endif /* _LINUX_PAGE_FLAGS_LAYOUT */