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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 88D36C3A59B for ; Fri, 30 Aug 2019 23:57:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 52E18208E4 for ; Fri, 30 Aug 2019 23:57:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=pensando.io header.i=@pensando.io header.b="WMKWfiuB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728275AbfH3X5p (ORCPT ); Fri, 30 Aug 2019 19:57:45 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:34969 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728242AbfH3X5p (ORCPT ); Fri, 30 Aug 2019 19:57:45 -0400 Received: by mail-pg1-f194.google.com with SMTP id n4so4303019pgv.2 for ; Fri, 30 Aug 2019 16:57:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pensando.io; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=vbfHQCbQOz6pXaMD1WdGmyVXpNXS38xujbQ+/0JQkQM=; b=WMKWfiuBvH5lMjSQEzDAk5wOOd4aGxdQtY+6NmQT/fB9RTqFr/PPXO+mUlgKs6w35v Cs9VGi6+VIsh2t02t6igMIdjhFRA0w0GFE6t1+xFQm8xF1x6vK8Lrmc55uQl/pb0N1sl T+cWiA+BCKSmOxJZZmoHBHLl0ujBAKVkv6PtDR43Mk1ybUwawEWu7/Ksi02zkBcXqCHR vw3+niyvhN1Tah3eMNBqwPK0BdTP4ZffNIvImkikbXtnQZnxqKwJSKnMCnfUbKBQ6sgC lxqDvtEu4pjh2Fn8n2BmS30OVSp8bANnS+sR25t80GpBAOAUgM6voLnc0P/GKqm9w6CN nOjw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=vbfHQCbQOz6pXaMD1WdGmyVXpNXS38xujbQ+/0JQkQM=; b=FrSbX9Ofw6afNigaaGNH/g0QkwvWIFBuNRyjH1cebQr8uWFK7DyiHvfIdfr/QWxuhe 6q7JQ1SSbgHhS4aTJGQlgLLpHAKtSwnRCjAtyL3VQ2Ja3Qg8KNQyyDcnBpi3RfUbZ9nb yVGErU8t9HizUXLYtwHUxYFc0WOZMUFoGbGs/pG2MipyFe5IKXED6nlH0GVzUaFmZh5J yLNT7pv5PQ2MFRdpmSH9JxFO+od1trX9gYLw9NjHBccIG3eGpfi8pkS1iPHISq+raWvL Kfs/szDRqLy5eEmiS/79LbeTEvqw45DANIpy5hFXDYTvKsNDnxx2EWFbR2nA15Zo5HWe ZmPg== X-Gm-Message-State: APjAAAX7CouJB4As0WOi+Qag63uuZkLUCqw6VGdbuJpYguwWsFnQxp8r dqazdIT6ckpkny8DRXDWAMWWfCWoF4A= X-Google-Smtp-Source: APXvYqw0k5tlWlbqs7drBHLQwYkq9a+fObw8KXDFfk59hnyQgyajK/AzOvl/rwHX5+AmNXkqAX9KiA== X-Received: by 2002:a63:c304:: with SMTP id c4mr14821840pgd.126.1567209464341; Fri, 30 Aug 2019 16:57:44 -0700 (PDT) Received: from Shannons-MacBook-Pro.local ([12.1.37.26]) by smtp.gmail.com with ESMTPSA id t9sm6152686pgj.89.2019.08.30.16.57.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 30 Aug 2019 16:57:43 -0700 (PDT) Subject: Re: [PATCH v6 net-next 15/19] ionic: Add Tx and Rx handling To: Jakub Kicinski Cc: netdev@vger.kernel.org, davem@davemloft.net References: <20190829182720.68419-1-snelson@pensando.io> <20190829182720.68419-16-snelson@pensando.io> <20190829161852.1705d770@cakuba.netronome.com> From: Shannon Nelson Message-ID: Date: Fri, 30 Aug 2019 16:57:41 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190829161852.1705d770@cakuba.netronome.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 8/29/19 4:18 PM, Jakub Kicinski wrote: > On Thu, 29 Aug 2019 11:27:16 -0700, Shannon Nelson wrote: >> +netdev_tx_t ionic_start_xmit(struct sk_buff *skb, struct net_device *netdev) >> +{ >> + u16 queue_index = skb_get_queue_mapping(skb); >> + struct ionic_lif *lif = netdev_priv(netdev); >> + struct ionic_queue *q; >> + int ndescs; >> + int err; >> + >> + if (unlikely(!test_bit(IONIC_LIF_UP, lif->state))) { >> + dev_kfree_skb(skb); >> + return NETDEV_TX_OK; >> + } >> + >> + if (likely(lif_to_txqcq(lif, queue_index))) >> + q = lif_to_txq(lif, queue_index); >> + else >> + q = lif_to_txq(lif, 0); >> + >> + ndescs = ionic_tx_descs_needed(q, skb); >> + if (ndescs < 0) >> + goto err_out_drop; >> + >> + if (!ionic_q_has_space(q, ndescs)) { > You should stop the queue in advance, whenever you can't ensure that a > max size frame can be placed on the ring. Requeuing is very expensive > so modern drivers should try to never return NETDEV_TX_BUSY Yes, I see how that's been done in nfp - good idea. > >> + netif_stop_subqueue(netdev, queue_index); >> + q->stop++; >> + >> + /* Might race with ionic_tx_clean, check again */ >> + smp_rmb(); >> + if (ionic_q_has_space(q, ndescs)) { >> + netif_wake_subqueue(netdev, queue_index); >> + q->wake++; >> + } else { >> + return NETDEV_TX_BUSY; >> + } >> + } >> + >> + if (skb_is_gso(skb)) >> + err = ionic_tx_tso(q, skb); >> + else >> + err = ionic_tx(q, skb); >> + >> + if (err) >> + goto err_out_drop; >> + >> + return NETDEV_TX_OK; >> + >> +err_out_drop: >> + netif_stop_subqueue(netdev, queue_index); > This stopping of the queue is suspicious, if ionic_tx() fails there's > no guarantee the queue will ever be woken up, no? Yes, that does look odd.  If there isn't a new descriptor with an skb in the queue, it won't get cleaned and reenabled in the Tx clean. sln > >> + q->stop++; >> + q->drop++; >> + dev_kfree_skb(skb); >> + return NETDEV_TX_OK; >> +}