diff mbox

[06/26] netfilter: conntrack: align nf_conn on cacheline boundary

Message ID 1467815048-2240-7-git-send-email-pablo@netfilter.org
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Pablo Neira Ayuso July 6, 2016, 2:23 p.m. UTC 
From: Florian Westphal <fw@strlen.de>

increases struct size by 32 bytes (288 -> 320), but it is the right thing,
else any attempt to (re-)arrange nf_conn members by cacheline won't work.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_conntrack_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

David Laight July 6, 2016, 2:45 p.m. UTC | #1 
From: Pablo Neira Ayuso
> Sent: 06 July 2016 15:24
> From: Florian Westphal <fw@strlen.de>
> 
> increases struct size by 32 bytes (288 -> 320), but it is the right thing,
> else any attempt to (re-)arrange nf_conn members by cacheline won't work.
...
>  	nf_conntrack_cachep = kmem_cache_create("nf_conntrack",
>  						sizeof(struct nf_conn), 0,
> -						SLAB_DESTROY_BY_RCU, NULL);
> +						SLAB_DESTROY_BY_RCU | SLAB_HWCACHE_ALIGN, NULL);

What happens on systems with cache lines that are longer than 64 bytes?
(I'm pretty sure some ppc systems have long cache lines.)

	David
Florian Westphal July 6, 2016, 3:01 p.m. UTC | #2 
David Laight <David.Laight@ACULAB.COM> wrote:
> From: Pablo Neira Ayuso
> > Sent: 06 July 2016 15:24
> > From: Florian Westphal <fw@strlen.de>
> > 
> > increases struct size by 32 bytes (288 -> 320), but it is the right thing,
> > else any attempt to (re-)arrange nf_conn members by cacheline won't work.
> ...
> >  	nf_conntrack_cachep = kmem_cache_create("nf_conntrack",
> >  						sizeof(struct nf_conn), 0,
> > -						SLAB_DESTROY_BY_RCU, NULL);
> > +						SLAB_DESTROY_BY_RCU | SLAB_HWCACHE_ALIGN, NULL);
> 
> What happens on systems with cache lines that are longer than 64 bytes?

Sorry, I don't have a secret decoder ring.

HWCACHE_ALIGN is used for several other net slab caches, including
skbuff, so why is this a problem here?
diff mbox

Patch

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index db2312e..2903bb4 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1731,7 +1731,7 @@  int nf_conntrack_init_start(void)
 
 	nf_conntrack_cachep = kmem_cache_create("nf_conntrack",
 						sizeof(struct nf_conn), 0,
-						SLAB_DESTROY_BY_RCU, NULL);
+						SLAB_DESTROY_BY_RCU | SLAB_HWCACHE_ALIGN, NULL);
 	if (!nf_conntrack_cachep)
 		goto err_cachep;