diff mbox

[03/12] netfilter: x_tables: align per cpu xt_counter

Message ID 1434734269-4545-4-git-send-email-pablo@netfilter.org
State Awaiting Upstream
Delegated to: Pablo Neira
Headers show

Commit Message

Pablo Neira Ayuso June 19, 2015, 5:17 p.m. UTC 
From: Eric Dumazet <edumazet@google.com>

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@google.com>
Cc: Florian Westphal <fw@strlen.de>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 include/linux/netfilter/x_tables.h |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Comments

David Laight June 22, 2015, 11:49 a.m. UTC | #1 
From: Pablo Neira Ayuso
> Sent: 19 June 2015 18:18
> From: Eric Dumazet <edumazet@google.com>
> 
> 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.

You could allocate a wrapper structure that contains xt_counter
and is itself marked __align(16).

	David

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Eric Dumazet June 22, 2015, 1:27 p.m. UTC | #2 
On Mon, 2015-06-22 at 11:49 +0000, David Laight wrote:
> From: Pablo Neira Ayuso
> > Sent: 19 June 2015 18:18
> > From: Eric Dumazet <edumazet@google.com>
> > 
> > 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.
> 
> You could allocate a wrapper structure that contains xt_counter
> and is itself marked __align(16).

Sure. I took one solution, out of multiple ones.


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diff mbox

Patch

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;