On Friday 10 November 2006 07:48, Andi Kleen wrote:
> Have you checked how much the code .text size changes because
> of the pointer reference? If it's a lot phys_to_nid might need to
> be out of lined.
Here I have also big numbers on pfn_to_page(), on a machine with mapsize=1
(NUMA kernel, but one node)
oprofile results L1_AND_L2_DTLB_MISSES /usr/src/linux-2.6.18/vmlinux
Counted L1_AND_L2_DTLB_MISSES events (L1 and L2 DTLB misses) with a unit mask
of 0x00 (No unit mask) count 10000
ffffffff80258fa0 <pfn_to_page>: /* pfn_to_page total: 48433 0.4914 */
So adding yet another indirection (to a another cache line) might hurt.
Therefore I suggest to use a structure like that :
struct memnode {
int shift;
unsigned int mapsize; /* no need to use 8 bytes here */
u8 *map;
u8 embedded_map[64-8]; /* total size = 64 bytes */
} ____cacheline_aligned;
and make memnode.map point to memnode.embedded_map if mapsize <= 56 ?
This way, most AMD64 dual/quad processors wont waste a full PAGE to store few
bytes in it, and should use only one cache line.
Thank you
Eric
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