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Commit 529a3404 authored by Eric Dumazet's avatar Eric Dumazet Committed by Linus Torvalds
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[PATCH] x86_64: Optimize NUMA node hash function 



Compute the highest possible value for memnode_shift, in order to reduce
footprint of memnodemap[] to the minimum, thus making all users
(phys_to_nid(), kfree()), more cache friendly.

Before the patch :

 Node 0 MemBase 0000000000000000 Limit 00000001ffffffff
 Node 1 MemBase 0000000200000000 Limit 00000003ffffffff
 Using 23 for the hash shift. Max adder is 3ffffffff

After the patch :

 Node 0 MemBase 0000000000000000 Limit 00000001ffffffff
 Node 1 MemBase 0000000200000000 Limit 00000003ffffffff
 Using 33 for the hash shift.

In this case, only 2 bytes of memnodemap[] are used, instead of 2048

Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e4e5d324

arch/x86_64/mm/numa.c

+43 −24
Original line number Diff line number Diff line
@@ -38,38 +38,57 @@ cpumask_t node_to_cpumask[MAX_NUMNODES] __read_mostly; 


int numa_off __initdata;



int __init compute_hash_shift(struct node *nodes, int numnodes)



/*

 * Given a shift value, try to populate memnodemap[]

 * Returns :

 * 1 if OK

 * 0 if memnodmap[] too small (of shift too small)

 * -1 if node overlap or lost ram (shift too big)

 */

static int __init populate_memnodemap(

	const struct node *nodes, int numnodes, int shift)

{

	int i; 

	int shift = 20;

	unsigned long addr,maxend=0;

	int res = -1;

	unsigned long addr, end;



	memset(memnodemap, 0xff, sizeof(memnodemap));

	for (i = 0; i < numnodes; i++) {

		addr = nodes[i].start;

		end = nodes[i].end;

		if (addr >= end)

			continue;

		if ((end >> shift) >= NODEMAPSIZE)

			return 0;

		do {

			if (memnodemap[addr >> shift] != 0xff)

				return -1;

			memnodemap[addr >> shift] = i;

			addr += (1 << shift);

		} while (addr < end);

		res = 1;

	} 

	return res;

}



	for (i = 0; i < numnodes; i++)

		if ((nodes[i].start != nodes[i].end) && (nodes[i].end > maxend))

				maxend = nodes[i].end;

int __init compute_hash_shift(struct node *nodes, int numnodes)

{

	int shift = 20;



	while ((1UL << shift) <  (maxend / NODEMAPSIZE))

	while (populate_memnodemap(nodes, numnodes, shift + 1) >= 0)

		shift++;



	printk (KERN_DEBUG"Using %d for the hash shift. Max adder is %lx \n",

			shift,maxend);

	memset(memnodemap,0xff,sizeof(*memnodemap) * NODEMAPSIZE);

	for (i = 0; i < numnodes; i++) {

		if (nodes[i].start == nodes[i].end)

			continue;

		for (addr = nodes[i].start;

		     addr < nodes[i].end;

		     addr += (1UL << shift)) {

			if (memnodemap[addr >> shift] != 0xff) {

	printk(KERN_DEBUG "Using %d for the hash shift.\n",

		shift);



	if (populate_memnodemap(nodes, numnodes, shift) != 1) {

		printk(KERN_INFO

	"Your memory is not aligned you need to rebuild your kernel "

	"with a bigger NODEMAPSIZE shift=%d adder=%lu\n",

					shift,addr);

	"with a bigger NODEMAPSIZE shift=%d\n",

			shift);

		return -1;

	}

			memnodemap[addr >> shift] = i;

		} 

	} 

	return shift;

}