linux-kernel - [143/156] skbuff: remove unused dma_head & dma

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Message-Id: <20100330224853.402913400@linux.site>
Date:	Tue, 30 Mar 2010 15:42:57 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Alexander Duyck <alexander.h.duyck@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [143/156] skbuff: remove unused dma_head & dma_maps fields

2.6.33-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Alexander Duyck <alexander.h.duyck@...el.com>

[ Upstream commit 03e6d819c2cb2cc8ce5642669a0a7c72336ee7a2 ]

The dma map fields in the skb_shared_info structure no longer has any users
and can be dropped since it is making the skb_shared_info unecessarily larger.

Running slabtop show that we were using 4K slabs for the skb->head on x86_64 w/
an allocation size of 1522.  It turns out that the dma_head and dma_maps array
made skb_shared large enough that we had crossed over the 2k boundary with
standard frames and as such we were using 4k blocks of memory for all skbs.

Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Acked-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 include/linux/skbuff.h |    6 ------
 1 file changed, 6 deletions(-)

--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -190,9 +190,6 @@ struct skb_shared_info {
 	atomic_t	dataref;
 	unsigned short	nr_frags;
 	unsigned short	gso_size;
-#ifdef CONFIG_HAS_DMA
-	dma_addr_t	dma_head;
-#endif
 	/* Warning: this field is not always filled in (UFO)! */
 	unsigned short	gso_segs;
 	unsigned short  gso_type;
@@ -201,9 +198,6 @@ struct skb_shared_info {
 	struct sk_buff	*frag_list;
 	struct skb_shared_hwtstamps hwtstamps;
 	skb_frag_t	frags[MAX_SKB_FRAGS];
-#ifdef CONFIG_HAS_DMA
-	dma_addr_t	dma_maps[MAX_SKB_FRAGS];
-#endif
 	/* Intermediate layers must ensure that destructor_arg
 	 * remains valid until skb destructor */
 	void *		destructor_arg;

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