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=-11.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 3DAC8C433E7 for ; Wed, 2 Sep 2020 14:36:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2655620767 for ; Wed, 2 Sep 2020 14:36:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728104AbgIBOgz (ORCPT ); Wed, 2 Sep 2020 10:36:55 -0400 Received: from dispatch1-us1.ppe-hosted.com ([148.163.129.52]:56702 "EHLO dispatch1-us1.ppe-hosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726285AbgIBOgo (ORCPT ); Wed, 2 Sep 2020 10:36:44 -0400 Received: from mx1-us1.ppe-hosted.com (unknown [10.7.65.62]) by dispatch1-us1.ppe-hosted.com (PPE Hosted ESMTP Server) with ESMTP id 54E0B60155; Wed, 2 Sep 2020 14:36:44 +0000 (UTC) Received: from us4-mdac16-21.ut7.mdlocal (unknown [10.7.65.245]) by mx1-us1.ppe-hosted.com (PPE Hosted ESMTP Server) with ESMTP id B0F9F800B4; Wed, 2 Sep 2020 14:36:43 +0000 (UTC) X-Virus-Scanned: Proofpoint Essentials engine Received: from mx1-us1.ppe-hosted.com (unknown [10.7.65.175]) by mx1-us1.ppe-hosted.com (PPE Hosted ESMTP Server) with ESMTPS id 2DB8E2800A7; Wed, 2 Sep 2020 14:36:42 +0000 (UTC) Received: from webmail.solarflare.com (uk.solarflare.com [193.34.186.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mx1-us1.ppe-hosted.com (PPE Hosted ESMTP Server) with ESMTPS id 678817000AC; Wed, 2 Sep 2020 14:36:42 +0000 (UTC) Received: from [10.17.20.203] (10.17.20.203) by ukex01.SolarFlarecom.com (10.17.10.4) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 2 Sep 2020 15:36:26 +0100 From: Edward Cree Subject: [PATCH net-next 2/5] sfc: use tx_queue->old_read_count in EF100 TX path To: , CC: References: Message-ID: <6c1deaca-102d-40bb-5ffe-9507f01a8788@solarflare.com> Date: Wed, 2 Sep 2020 15:36:22 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-GB Content-Transfer-Encoding: 7bit X-Originating-IP: [10.17.20.203] X-ClientProxiedBy: ocex03.SolarFlarecom.com (10.20.40.36) To ukex01.SolarFlarecom.com (10.17.10.4) X-TM-AS-Product-Ver: SMEX-12.5.0.1300-8.6.1012-25640.003 X-TM-AS-Result: No-4.229900-8.000000-10 X-TMASE-MatchedRID: B4VcMIpPJ800hZmSa+ztRMzSKGx9g8xheouvej40T4gd0WOKRkwsh1ym Rv3NQjsE4aBLis6ititw5T4Iaj538mJZXQNDzktSMiMrbc70Pfdc1jwHBugxQIxRWJphhsrcrzM i7F2pFcpny03aprSl5E4r6tWjD8M+YAgEin+2ERDiHyvyXeXh5sHWhOU1PTVYNCjbDif9OIzSJJ cbp1Y+W8Q1xvPMAvfZDvP/tkcd5GOMQmg2+WN4O095wQijrwBLfS0Ip2eEHny+qryzYw2E8Jkw8 KdMzN86KrauXd3MZDUYmhvFbntAL6TRb8tZ3yWI26UtHqFTik1hKMIvwkzgVs1EcebW768Tg5qe iqlH6shWa9YJ+3+CBf2iSrkndGlHB+RsQUnQHf3jCHw9x1eKskODDY5/BuEsoxrk6Q2mIeSJ+wv 7oJjhGclmajRS8yWxQwymtxuJ6y0= X-TM-AS-User-Approved-Sender: Yes X-TM-AS-User-Blocked-Sender: No X-TMASE-Result: 10--4.229900-8.000000 X-TMASE-Version: SMEX-12.5.0.1300-8.6.1012-25640.003 X-MDID: 1599057403-2gRDV7kY_GZZ Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org As in the Siena/EF10 case, it minimises cacheline ping-pong between the TX and completion paths. Signed-off-by: Edward Cree --- drivers/net/ethernet/sfc/ef100_tx.c | 8 ++++++-- drivers/net/ethernet/sfc/net_driver.h | 14 ++++++++++++++ 2 files changed, 20 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/sfc/ef100_tx.c b/drivers/net/ethernet/sfc/ef100_tx.c index a09546e43408..47d67b1e379b 100644 --- a/drivers/net/ethernet/sfc/ef100_tx.c +++ b/drivers/net/ethernet/sfc/ef100_tx.c @@ -359,15 +359,19 @@ int ef100_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb) goto err; ef100_tx_make_descriptors(tx_queue, skb, segments); - fill_level = efx_channel_tx_fill_level(tx_queue->channel); + fill_level = efx_channel_tx_old_fill_level(tx_queue->channel); if (fill_level > efx->txq_stop_thresh) { + struct efx_tx_queue *txq2; + netif_tx_stop_queue(tx_queue->core_txq); /* Re-read after a memory barrier in case we've raced with * the completion path. Otherwise there's a danger we'll never * restart the queue if all completions have just happened. */ smp_mb(); - fill_level = efx_channel_tx_fill_level(tx_queue->channel); + efx_for_each_channel_tx_queue(txq2, tx_queue->channel) + txq2->old_read_count = READ_ONCE(txq2->read_count); + fill_level = efx_channel_tx_old_fill_level(tx_queue->channel); if (fill_level < efx->txq_stop_thresh) netif_tx_start_queue(tx_queue->core_txq); } diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h index 338ebb0402be..2358d35bffb5 100644 --- a/drivers/net/ethernet/sfc/net_driver.h +++ b/drivers/net/ethernet/sfc/net_driver.h @@ -1692,6 +1692,20 @@ efx_channel_tx_fill_level(struct efx_channel *channel) return fill_level; } +/* Conservative approximation of efx_channel_tx_fill_level using cached value */ +static inline unsigned int +efx_channel_tx_old_fill_level(struct efx_channel *channel) +{ + struct efx_tx_queue *tx_queue; + unsigned int fill_level = 0; + + efx_for_each_channel_tx_queue(tx_queue, channel) + fill_level = max(fill_level, + tx_queue->insert_count - tx_queue->old_read_count); + + return fill_level; +} + /* Get all supported features. * If a feature is not fixed, it is present in hw_features. * If a feature is fixed, it does not present in hw_features, but