Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261698AbUKSXaS (ORCPT ); Fri, 19 Nov 2004 18:30:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261637AbUKSX1z (ORCPT ); Fri, 19 Nov 2004 18:27:55 -0500 Received: from mta1.cl.cam.ac.uk ([128.232.0.15]:6855 "EHLO mta1.cl.cam.ac.uk") by vger.kernel.org with ESMTP id S261652AbUKSXZS (ORCPT ); Fri, 19 Nov 2004 18:25:18 -0500 To: Ian Pratt cc: linux-kernel@vger.kernel.org, Steven.Hand@cl.cam.ac.uk, Christian.Limpach@cl.cam.ac.uk, Keir.Fraser@cl.cam.ac.uk, davem@redhat.com Subject: [6/7] Xen VMM patch set : add alloc_skb_from_cache In-reply-to: Your message of "Fri, 19 Nov 2004 23:16:33 GMT." Date: Fri, 19 Nov 2004 23:25:07 +0000 From: Ian Pratt Message-Id: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3840 Lines: 111 This patch adds a new alloc_skb_from_cache function. This serves two purposes: firstly, we like to allocate skb's with page-sized data fragements as this means we can do zero-copy transfer of network buffers between guest operating systems. Secondly, it enables us to have a cache of pages that have been used for network buffers that we can be more lax about scrubbing when they change VM ownership (since they could be sniffed on the wire). Signed-off-by: ian.pratt@cl.cam.ac.uk --- diff -Nurp pristine-linux-2.6.10-rc2/net/core/skbuff.c tmp-linux-2.6.10-rc2-xen.patch/net/core/skbuff.c --- pristine-linux-2.6.10-rc2/net/core/skbuff.c 2004-11-15 01:28:14.000000000 +0000 +++ tmp-linux-2.6.10-rc2-xen.patch/net/core/skbuff.c 2004-11-19 16:42:55.000000000 +0000 @@ -163,6 +163,59 @@ nodata: goto out; } +/** + * alloc_skb_from_cache - allocate a network buffer + * @cp: kmem_cache from which to allocate the data area + * (object size must be big enough for @size bytes + skb overheads) + * @size: size to allocate + * @gfp_mask: allocation mask + * + * Allocate a new &sk_buff. The returned buffer has no headroom and a + * tail room of size bytes. The object has a reference count of one. + * The return is the buffer. On a failure the return is %NULL. + * + * Buffers may only be allocated from interrupts using a @gfp_mask of + * %GFP_ATOMIC. + */ +struct sk_buff *alloc_skb_from_cache(kmem_cache_t *cp, + unsigned int size, int gfp_mask) +{ + struct sk_buff *skb; + u8 *data; + + /* Get the HEAD */ + skb = kmem_cache_alloc(skbuff_head_cache, + gfp_mask & ~__GFP_DMA); + if (!skb) + goto out; + + /* Get the DATA. */ + size = SKB_DATA_ALIGN(size); + data = kmem_cache_alloc(cp, gfp_mask); + if (!data) + goto nodata; + + memset(skb, 0, offsetof(struct sk_buff, truesize)); + skb->truesize = size + sizeof(struct sk_buff); + atomic_set(&skb->users, 1); + skb->head = data; + skb->data = data; + skb->tail = data; + skb->end = data + size; + + atomic_set(&(skb_shinfo(skb)->dataref), 1); + skb_shinfo(skb)->nr_frags = 0; + skb_shinfo(skb)->tso_size = 0; + skb_shinfo(skb)->tso_segs = 0; + skb_shinfo(skb)->frag_list = NULL; +out: + return skb; +nodata: + kmem_cache_free(skbuff_head_cache, skb); + skb = NULL; + goto out; +} + static void skb_drop_fraglist(struct sk_buff *skb) { diff -Nurp pristine-linux-2.6.10-rc2/include/linux/skbuff.h tmp-linux-2.6.10-rc2-xen.patch/include/linux/skbuff.h --- pristine-linux-2.6.10-rc2/include/linux/skbuff.h 2004-11-15 01:29:01.000000000 +0000 +++ tmp-linux-2.6.10-rc2-xen.patch/include/linux/skbuff.h 2004-11-18 19:58:13.000000000 +0000 @@ -292,6 +292,8 @@ struct sk_buff { extern void __kfree_skb(struct sk_buff *skb); extern struct sk_buff *alloc_skb(unsigned int size, int priority); +extern struct sk_buff *alloc_skb_from_cache(kmem_cache_t *cp, + unsigned int size, int priority); extern void kfree_skbmem(struct sk_buff *skb); extern struct sk_buff *skb_clone(struct sk_buff *skb, int priority); extern struct sk_buff *skb_copy(const struct sk_buff *skb, int priority); @@ -935,6 +937,7 @@ static inline void __skb_queue_purge(str * * %NULL is returned in there is no free memory. */ +#ifndef CONFIG_HAVE_ARCH_DEV_ALLOC_SKB static inline struct sk_buff *__dev_alloc_skb(unsigned int length, int gfp_mask) { @@ -943,6 +946,9 @@ static inline struct sk_buff *__dev_allo skb_reserve(skb, 16); return skb; } +#else +extern struct sk_buff *__dev_alloc_skb(unsigned int length, int gfp_mask); +#endif /** * dev_alloc_skb - allocate an skbuff for sending - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/