From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: [PATCH v3 2/6] net: move destructor_arg to the front of sk_buff. Date: Wed, 25 Jan 2012 12:27:10 +0000 Message-ID: <1327494434-21566-2-git-send-email-ian.campbell@citrix.com> References: <1327494389.24561.316.camel@zakaz.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain Cc: Ian Campbell , "David S. Miller" , Eric Dumazet To: netdev@vger.kernel.org Return-path: Received: from smtp.citrix.com ([66.165.176.89]:44228 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752843Ab2AYM1U (ORCPT ); Wed, 25 Jan 2012 07:27:20 -0500 In-Reply-To: <1327494389.24561.316.camel@zakaz.uk.xensource.com> Sender: netdev-owner@vger.kernel.org List-ID: As of the previous patch we align the end (rather than the start) of the struct to a cache line and so, with 32 and 64 byte cache lines and the shinfo size increase from the next patch, the first 8 bytes of the struct end up on a different cache line to the rest of it so make sure it is something relatively unimportant to avoid hitting an extra cache line on hot operations such as kfree_skb. Signed-off-by: Ian Campbell Cc: "David S. Miller" Cc: Eric Dumazet --- include/linux/skbuff.h | 15 ++++++++++----- net/core/skbuff.c | 5 ++++- 2 files changed, 14 insertions(+), 6 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index f04333b..7b82ed1 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -242,6 +242,15 @@ struct ubuf_info { * the end of the header data, ie. at skb->end. */ struct skb_shared_info { + /* Intermediate layers must ensure that destructor_arg + * remains valid until skb destructor */ + void *destructor_arg; + + /* + * Warning: all fields from here until dataref are cleared in + * __alloc_skb() + * + */ unsigned char nr_frags; __u8 tx_flags; unsigned short gso_size; @@ -253,14 +262,10 @@ struct skb_shared_info { __be32 ip6_frag_id; /* - * Warning : all fields before dataref are cleared in __alloc_skb() + * Warning: all fields before dataref are cleared in __alloc_skb() */ atomic_t dataref; - /* Intermediate layers must ensure that destructor_arg - * remains valid until skb destructor */ - void * destructor_arg; - /* must be last field, see pskb_expand_head() */ skb_frag_t frags[MAX_SKB_FRAGS]; }; diff --git a/net/core/skbuff.c b/net/core/skbuff.c index b6de604..934a9b4 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -219,7 +219,10 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, /* make sure we initialize shinfo sequentially */ shinfo = skb_shinfo(skb); - memset(shinfo, 0, offsetof(struct skb_shared_info, dataref)); + + memset(&shinfo->nr_frags, 0, + offsetof(struct skb_shared_info, dataref) + - offsetof(struct skb_shared_info, nr_frags)); atomic_set(&shinfo->dataref, 1); kmemcheck_annotate_variable(shinfo->destructor_arg); -- 1.7.2.5