From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C52C5C28CF6 for ; Wed, 1 Aug 2018 17:40:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7636E208A3 for ; Wed, 1 Aug 2018 17:40:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7636E208A3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2436486AbeHAT0B (ORCPT ); Wed, 1 Aug 2018 15:26:01 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:52926 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2436515AbeHATSh (ORCPT ); Wed, 1 Aug 2018 15:18:37 -0400 Received: from localhost (D57E6652.static.ziggozakelijk.nl [213.126.102.82]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 6EC44E2B; Wed, 1 Aug 2018 16:53:37 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Juergen Gross , Boris Ostrovsky , "David S. Miller" , Sasha Levin Subject: [PATCH 4.17 019/336] xen/netfront: raise max number of slots in xennet_get_responses() Date: Wed, 1 Aug 2018 18:45:54 +0200 Message-Id: <20180801165029.727882842@linuxfoundation.org> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180801165028.930831994@linuxfoundation.org> References: <20180801165028.930831994@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Juergen Gross [ Upstream commit 57f230ab04d2910a06d17d988f1c4d7586a59113 ] The max number of slots used in xennet_get_responses() is set to MAX_SKB_FRAGS + (rx->status <= RX_COPY_THRESHOLD). In old kernel-xen MAX_SKB_FRAGS was 18, while nowadays it is 17. This difference is resulting in frequent messages "too many slots" and a reduced network throughput for some workloads (factor 10 below that of a kernel-xen based guest). Replacing MAX_SKB_FRAGS by XEN_NETIF_NR_SLOTS_MIN for calculation of the max number of slots to use solves that problem (tests showed no more messages "too many slots" and throughput was as high as with the kernel-xen based guest system). Replace MAX_SKB_FRAGS-2 by XEN_NETIF_NR_SLOTS_MIN-1 in netfront_tx_slot_available() for making it clearer what is really being tested without actually modifying the tested value. Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky Signed-off-by: David S. Miller Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/net/xen-netfront.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -239,7 +239,7 @@ static void rx_refill_timeout(struct tim static int netfront_tx_slot_available(struct netfront_queue *queue) { return (queue->tx.req_prod_pvt - queue->tx.rsp_cons) < - (NET_TX_RING_SIZE - MAX_SKB_FRAGS - 2); + (NET_TX_RING_SIZE - XEN_NETIF_NR_SLOTS_MIN - 1); } static void xennet_maybe_wake_tx(struct netfront_queue *queue) @@ -790,7 +790,7 @@ static int xennet_get_responses(struct n RING_IDX cons = queue->rx.rsp_cons; struct sk_buff *skb = xennet_get_rx_skb(queue, cons); grant_ref_t ref = xennet_get_rx_ref(queue, cons); - int max = MAX_SKB_FRAGS + (rx->status <= RX_COPY_THRESHOLD); + int max = XEN_NETIF_NR_SLOTS_MIN + (rx->status <= RX_COPY_THRESHOLD); int slots = 1; int err = 0; unsigned long ret;