Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932814Ab2FGETw (ORCPT ); Thu, 7 Jun 2012 00:19:52 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:63306 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932795Ab2FGETs (ORCPT ); Thu, 7 Jun 2012 00:19:48 -0400 Message-Id: <20120607040344.597358152@linuxfoundation.org> User-Agent: quilt/0.60-19.1 Date: Thu, 07 Jun 2012 13:04:33 +0900 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Felix Fietkau , Eric Dumazet , "David S. Miller" Subject: [ 57/82] skb: avoid unnecessary reallocations in __skb_cow In-Reply-To: <20120607041406.GA13233@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1540 Lines: 46 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Felix Fietkau [ Upstream commit 617c8c11236716dcbda877e764b7bf37c6fd8063 ] At the beginning of __skb_cow, headroom gets set to a minimum of NET_SKB_PAD. This causes unnecessary reallocations if the buffer was not cloned and the headroom is just below NET_SKB_PAD, but still more than the amount requested by the caller. This was showing up frequently in my tests on VLAN tx, where vlan_insert_tag calls skb_cow_head(skb, VLAN_HLEN). Locally generated packets should have enough headroom, and for forward paths, we already have NET_SKB_PAD bytes of headroom, so we don't need to add any extra space here. Signed-off-by: Felix Fietkau Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- include/linux/skbuff.h | 2 -- 1 file changed, 2 deletions(-) --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1881,8 +1881,6 @@ static inline int __skb_cow(struct sk_bu { int delta = 0; - if (headroom < NET_SKB_PAD) - headroom = NET_SKB_PAD; if (headroom > skb_headroom(skb)) delta = headroom - skb_headroom(skb); -- 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/