netdev - [PATCH] skbuff: remove unused dma_head & dma

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Date:	Tue, 23 Mar 2010 23:40:50 -0700
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	davem@...emloft.net
Cc:	netdev@...r.kernel.org, gospo@...hat.com,
	Alexander Duyck <alexander.h.duyck@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: [PATCH] skbuff: remove unused dma_head & dma_maps fields

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

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>
---

 include/linux/skbuff.h |    6 ------
 1 files changed, 0 insertions(+), 6 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 03f816a..124f90c 100644
--- 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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