From: Eric Dumazet <edumazet@xxxxxxxxxx>
Let's force a 16 bytes alignment on xt_counter percpu allocations,
so that bytes and packets sit in same cache line.
xt_counter being exported to user space, we cannot add __align(16) on
the structure itself.
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Florian Westphal <fw@xxxxxxxxx>
Acked-by: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
include/linux/netfilter/x_tables.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h
index 95693c4..1c97a22 100644
--- a/include/linux/netfilter/x_tables.h
+++ b/include/linux/netfilter/x_tables.h
@@ -356,7 +356,8 @@ static inline unsigned long ifname_compare_aligned(const char *_a,
* so nothing needs to be done there.
*
* xt_percpu_counter_alloc returns the address of the percpu
- * counter, or 0 on !SMP.
+ * counter, or 0 on !SMP. We force an alignment of 16 bytes
+ * so that bytes/packets share a common cache line.
*
* Hence caller must use IS_ERR_VALUE to check for error, this
* allows us to return 0 for single core systems without forcing
@@ -365,7 +366,8 @@ static inline unsigned long ifname_compare_aligned(const char *_a,
static inline u64 xt_percpu_counter_alloc(void)
{
if (nr_cpu_ids > 1) {
- void __percpu *res = alloc_percpu(struct xt_counters);
+ void __percpu *res = __alloc_percpu(sizeof(struct xt_counters),
+ sizeof(struct xt_counters));
if (res == NULL)
return (u64) -ENOMEM;
--
1.7.10.4
--
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