Use sparsemem as the only memory model for UP, SMP and NUMA. Measurements
indicate that DISCONTIGMEM has a higher overhead than sparsemem. And
FLATMEMs benefits are minimal. So I think its best to simply standardize
on sparsemem.
Results of page allocator tests (test can be had via git from slab git
tree branch tests)
Measurements in cycle counts. 1000 allocations were performed and then the
average cycle count was calculated.
Order FlatMem Discontig SparseMem
0 639 665 641
1 567 647 593
2 679 774 692
3 763 967 781
4 961 1501 962
5 1356 2344 1392
6 2224 3982 2336
7 4869 7225 5074
8 12500 14048 12732
9 27926 28223 28165
10 58578 58714 58682
(Note that FlatMem is an SMP config and the rest NUMA configurations)
Memory use:
SMP Sparsemem
-------------
Kernel size:
text data bss dec hex filename
3849268 397739 1264856 5511863 541ab7 vmlinux
total used free shared buffers cached
Mem: 8242252 41164 8201088 0 352 11512
-/+ buffers/cache: 29300 8212952
Swap: 9775512 0 9775512
SMP Flatmem
-----------
Kernel size:
text data bss dec hex filename
3844612 397739 1264536 5506887 540747 vmlinux
So 4.5k growth in text size vs. FLATMEM.
total used free shared buffers cached
Mem: 8244052 40544 8203508 0 352 11484
-/+ buffers/cache: 28708 8215344
2k growth in overall memory use after boot.
NUMA discontig:
text data bss dec hex filename
3888124 470659 1276504 5635287 55fcd7 vmlinux
total used free shared buffers cached
Mem: 8256256 56908 8199348 0 352 11496
-/+ buffers/cache: 45060 8211196
Swap: 9775512 0 9775512
NUMA sparse:
text data bss dec hex filename
3896428 470659 1276824 5643911 561e87 vmlinux
8k text growth. Given that we fully inline virt_to_page and friends now
that is rather good.
total used free shared buffers cached
Mem: 8264720 57240 8207480 0 352 11516
-/+ buffers/cache: 45372 8219348
Swap: 9775512 0 9775512
The total available memory is increased by 8k.
This patch makes sparsemem the default and removes discontig and
flatmem support from x86.
[ akpm@linux-foundation.org: allnoconfig build fix ]
Acked-by: Andi Kleen <ak@suse.de>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
In x86_64 and i386 architectures most arrays that are sized using
NR_CPUS lay in local memory on node 0. Not only will most (99%?) of the
systems not use all the slots in these arrays, particularly when NR_CPUS
is increased to accommodate future very high cpu count systems, but a
number of cache lines are passed unnecessarily on the system bus when
these arrays are referenced by cpus on other nodes.
Typically, the values in these arrays are referenced by the cpu
accessing it's own values, though when passing IPI interrupts, the cpu
does access the data relevant to the targeted cpu/node. Of course, if
the referencing cpu is not on node 0, then the reference will still
require cross node exchanges of cache lines. A common use of this is
for an interrupt service routine to pass the interrupt to other cpus
local to that node.
Ideally, all the elements in these arrays should be moved to the per_cpu
data area. In some cases (such as x86_cpu_to_apicid) the array is
referenced before the per_cpu data areas are setup. In this case, a
static array is declared in the __initdata area and initialized by the
booting cpu (BSP). The values are then moved to the per_cpu area after
it is initialized and the original static array is freed with the rest
of the __initdata.
This patch:
Fix four instances where cpu_to_node is referenced by array instead of
via the cpu_to_node macro. This is preparation to moving it to the
per_cpu data area.
Signed-off-by: Mike Travis <travis@sgi.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Joe Perches