Eric Dumazet a écrit :
Andi Kleen a écrit :
Using memnode_shift=33 would access only 2 bytes from this
memnodemap[], touching fewer cache lines (well , one cache line).
kfree() and friends would be slightly faster, at least cache friendly.
Agreed. Please send a patch.
My previous patch was not correct. Couly you please review this second version.
[PATCH] NUMA,x86_64 :
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
Thank you
Signed-off-by: Eric Dumazet <[email protected]>
--- linux-2.6.14-rc2/arch/x86_64/mm/numa.c 2005-09-20 05:00:41.000000000 +0200
+++ linux-2.6.14-rc2-ed/arch/x86_64/mm/numa.c 2005-09-30 11:04:18.000000000 +0200
@@ -38,38 +38,57 @@
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;
-
- for (i = 0; i < numnodes; i++)
- if ((nodes[i].start != nodes[i].end) && (nodes[i].end > maxend))
- maxend = nodes[i].end;
+ int res = -1;
+ unsigned long addr, end;
- while ((1UL << shift) < (maxend / NODEMAPSIZE))
- shift++;
-
- printk (KERN_DEBUG"Using %d for the hash shift. Max adder is %lx \n",
- shift,maxend);
- memset(memnodemap,0xff,sizeof(*memnodemap) * NODEMAPSIZE);
+ memset(memnodemap, 0xff, sizeof(memnodemap));
for (i = 0; i < numnodes; i++) {
- if (nodes[i].start == nodes[i].end)
+ addr = nodes[i].start;
+ end = nodes[i].end;
+ if (addr >= end)
continue;
- for (addr = nodes[i].start;
- addr < nodes[i].end;
- addr += (1UL << shift)) {
- if (memnodemap[addr >> shift] != 0xff) {
- 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);
+ 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;
+}
+
+int __init compute_hash_shift(struct node *nodes, int numnodes)
+{
+ int shift = 20;
+
+ while (populate_memnodemap(nodes, numnodes, shift + 1) >= 0)
+ shift++;
+
+ 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\n",
+ shift);
+ return -1;
+ }
return shift;
}
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