From patchwork Thu Mar 27 12:56:12 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paul Durrant X-Patchwork-Id: 334326 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 0342D1400FA for ; Thu, 27 Mar 2014 23:56:40 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755285AbaC0M4f (ORCPT ); Thu, 27 Mar 2014 08:56:35 -0400 Received: from smtp.citrix.com ([66.165.176.89]:39776 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753943AbaC0M4e (ORCPT ); Thu, 27 Mar 2014 08:56:34 -0400 X-IronPort-AV: E=Sophos;i="4.97,742,1389744000"; d="scan'208";a="115424510" Received: from accessns.citrite.net (HELO FTLPEX01CL03.citrite.net) ([10.9.154.239]) by FTLPIPO01.CITRIX.COM with ESMTP; 27 Mar 2014 12:56:21 +0000 Received: from ukmail1.uk.xensource.com (10.80.16.128) by smtprelay.citrix.com (10.13.107.80) with Microsoft SMTP Server id 14.2.342.4; Thu, 27 Mar 2014 08:56:19 -0400 Received: from etemp.uk.xensource.com ([10.80.228.66] helo=etemp.uk.xensource.com.) by ukmail1.uk.xensource.com with esmtp (Exim 4.69) (envelope-from ) id 1WT9r1-0002ms-M4; Thu, 27 Mar 2014 12:56:19 +0000 From: Paul Durrant To: , CC: Paul Durrant , Ian Campbell , Wei Liu , Sander Eikelenboom Subject: [PATCH net v2 2/3] xen-netback: worse-case estimate in xenvif_rx_action is underestimating Date: Thu, 27 Mar 2014 12:56:12 +0000 Message-ID: <1395924973-42904-3-git-send-email-paul.durrant@citrix.com> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1395924973-42904-1-git-send-email-paul.durrant@citrix.com> References: <1395924973-42904-1-git-send-email-paul.durrant@citrix.com> MIME-Version: 1.0 X-DLP: MIA1 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The worse-case estimate for skb ring slot usage in xenvif_rx_action() fails to take fragment page_offset into account. The page_offset does, however, affect the number of times the fragmentation code calls start_new_rx_buffer() (i.e. consume another slot) and the worse-case should assume that will always return true. This patch adds the page_offset into the DIV_ROUND_UP for each frag. Signed-off-by: Paul Durrant Cc: Ian Campbell Cc: Wei Liu Cc: Sander Eikelenboom --- drivers/net/xen-netback/netback.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 72314c7..aa87ae8 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -493,8 +493,18 @@ static void xenvif_rx_action(struct xenvif *vif) PAGE_SIZE); for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { unsigned int size; + unsigned int offset; + size = skb_frag_size(&skb_shinfo(skb)->frags[i]); - max_slots_needed += DIV_ROUND_UP(size, PAGE_SIZE); + offset = skb_shinfo(skb)->frags[i].page_offset; + + /* For a worse-case estimate we need to factor in + * the fragment page offset as this will affect the + * number of times xenvif_gop_frag_copy() will + * call start_new_rx_buffer(). + */ + max_slots_needed += DIV_ROUND_UP(offset + size, + PAGE_SIZE); } if (skb_is_gso(skb) && (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4 ||