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From: Ian Campbell <ian.campbell@citrix.com>
To: netdev@vger.kernel.org
Cc: David Miller <davem@davemloft.net>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Wei Liu <wei.liu2@citrix.com>,
	xen-devel@lists.xen.org, Ian Campbell <ian.campbell@citrix.com>
Subject: [PATCH 05/10] net: move destructor_arg to the front of sk_buff.
Date: Tue, 10 Apr 2012 15:26:19 +0100	[thread overview]
Message-ID: <1334067984-7706-5-git-send-email-ian.campbell@citrix.com> (raw)
In-Reply-To: <1334067965.5394.22.camel@zakaz.uk.xensource.com>

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 <ian.campbell@citrix.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
---
 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 0ad6a46..f0ae39c 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -265,6 +265,15 @@ 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;
@@ -276,14 +285,10 @@ 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 d4e139e..b8a41d6 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -214,7 +214,10 @@ 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

  parent reply	other threads:[~2012-04-10 14:32 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-10 14:26 [PATCH v4 0/10] skb paged fragment destructors Ian Campbell
2012-04-10 14:26 ` [PATCH 01/10] net: add and use SKB_ALLOCSIZE Ian Campbell
2012-04-10 14:57   ` Eric Dumazet
2012-04-10 14:26 ` [PATCH 02/10] net: Use SKB_WITH_OVERHEAD in build_skb Ian Campbell
2012-04-10 14:58   ` Eric Dumazet
2012-04-10 14:26 ` [PATCH 03/10] chelsio: use SKB_WITH_OVERHEAD Ian Campbell
2012-04-10 14:59   ` Eric Dumazet
2012-04-10 14:26 ` [PATCH 04/10] net: pad skb data and shinfo as a whole rather than individually Ian Campbell
2012-04-10 15:01   ` Eric Dumazet
2012-04-10 14:26 ` Ian Campbell [this message]
2012-04-10 15:05   ` [PATCH 05/10] net: move destructor_arg to the front of sk_buff Eric Dumazet
2012-04-10 15:19     ` Ian Campbell
2012-04-10 18:33   ` Alexander Duyck
2012-04-10 18:41     ` Eric Dumazet
2012-04-10 19:15       ` Alexander Duyck
2012-04-11  8:00         ` Ian Campbell
2012-04-11 16:31           ` Alexander Duyck
2012-04-11 17:00             ` Ian Campbell
2012-04-11  8:20         ` Eric Dumazet
2012-04-11 16:05           ` Alexander Duyck
2012-04-11  7:56     ` Ian Campbell
2012-04-10 14:26 ` [PATCH 06/10] net: add support for per-paged-fragment destructors Ian Campbell
2012-04-26 20:44   ` [Xen-devel] " Konrad Rzeszutek Wilk
2012-04-10 14:26 ` [PATCH 07/10] net: only allow paged fragments with the same destructor to be coalesced Ian Campbell
2012-04-10 20:11   ` Ben Hutchings
2012-04-11  7:45     ` Ian Campbell
2012-04-10 14:26 ` [PATCH 08/10] net: add skb_orphan_frags to copy aside frags with destructors Ian Campbell
     [not found] ` <1334067965.5394.22.camel-o4Be2W7LfRlXesXXhkcM7miJhflN2719@public.gmane.org>
2012-04-10 14:26   ` [PATCH 09/10] net: add paged frag destructor support to kernel_sendpage Ian Campbell
2012-04-10 14:26   ` [PATCH 10/10] sunrpc: use SKB fragment destructors to delay completion until page is released by network stack Ian Campbell
2012-04-10 14:58 ` [PATCH v4 0/10] skb paged fragment destructors Michael S. Tsirkin
2012-04-10 15:00 ` Michael S. Tsirkin
2012-04-10 15:46 ` Bart Van Assche
2012-04-10 15:50   ` Ian Campbell
2012-04-11 10:02     ` Bart Van Assche

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