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flow : NUMA aware hash table allocation

IPSEC Applied Eric Dumazet 2 participants 2 messages Jan 1, 2008 – Jan 2, 2008

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Eric Dumazet

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#0 lore raw

Using __get_free_pages() has some drawbacks :

1) Not NUMA aware

2) 2^X page granularity :
On arches with big PAGE_SIZE, we waste some ram for each cpu.

(We currently use 1024 pointers, that is at most 8192 bytes, but PAGE_SIZE can be 65536 for example : With say 64 possible cpus, thats about 56*64 Kbytes that are wasted)

Using kmalloc_node() can help to solve these two points.

Signed-off-by Eric Dumazet <[email protected]>
 net/core/flow.c |   15 +++++----------
 1 files changed, 5 insertions(+), 10 deletions(-)
net/core/flow.c +5 -10
index a618f89..bcbbe2d 100644
@@ -311,18 +311,13 @@ void flow_cache_flush(void)
 static void __devinit flow_cache_cpu_prepare(int cpu)
 {
 	struct tasklet_struct *tasklet;
-	unsigned long order;
 
-	for (order = 0;
-	     (PAGE_SIZE << order) <
-		     (sizeof(struct flow_cache_entry *)*flow_hash_size);
-	     order++)
-		/* NOTHING */;
-
-	flow_table(cpu) = (struct flow_cache_entry **)
-		__get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
+	flow_table(cpu) = kmalloc_node(
+		sizeof(struct flow_cache_entry *) * flow_hash_size,
+		GFP_KERNEL | __GFP_ZERO,
+		cpu_to_node(cpu));
 	if (!flow_table(cpu))
-		panic("NET: failed to allocate flow cache order %lu\n", order);
+		panic("NET: failed to allocate flow cache for cpu %d\n", cpu);
 
 	flow_hash_rnd_recalc(cpu) = 1;
 	flow_count(cpu) = 0;
maintainer Applied
#1 lore raw

From: Eric Dumazet <[email protected]>
Date: Tue, 01 Jan 2008 13:44:15 +0100

Quoted 7 lines

Using __get_free_pages() has some drawbacks :

1) Not NUMA aware

2) 2^X page granularity :
On arches with big PAGE_SIZE, we waste some ram for each cpu.

Quoted 7 lines

(We currently use 1024 pointers, that is at most 8192 bytes, but PAGE_SIZE can be 65536 for example : With say 64 possible cpus, thats about 56*64 Kbytes that are wasted)

Using kmalloc_node() can help to solve these two points.

Signed-off-by Eric Dumazet <[email protected]>

Applied, thanks Eric.

It reminds me that flow_hash_shift should at some point be dynamically sized. However, currently the flow cache isn't so heavily used and there are more important fish to fry right now.