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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 09825C4338F for ; Fri, 13 Aug 2021 08:35:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D7C1E60F51 for ; Fri, 13 Aug 2021 08:35:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239235AbhHMIgO convert rfc822-to-8bit (ORCPT ); Fri, 13 Aug 2021 04:36:14 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:56111 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231127AbhHMIgN (ORCPT ); Fri, 13 Aug 2021 04:36:13 -0400 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-65-jWRYdI9NNEi-T8lGlFwTcQ-1; Fri, 13 Aug 2021 09:35:41 +0100 X-MC-Unique: jWRYdI9NNEi-T8lGlFwTcQ-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.23; Fri, 13 Aug 2021 09:35:39 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.023; Fri, 13 Aug 2021 09:35:39 +0100 From: David Laight To: 'Jakub Kicinski' , "davem@davemloft.net" CC: "michael.chan@broadcom.com" , "huangjw@broadcom.com" , "eddie.wai@broadcom.com" , "prashant@broadcom.com" , "gospo@broadcom.com" , "netdev@vger.kernel.org" , "edwin.peer@broadcom.com" Subject: RE: [PATCH net v2 3/4] bnxt: make sure xmit_more + errors does not miss doorbells Thread-Topic: [PATCH net v2 3/4] bnxt: make sure xmit_more + errors does not miss doorbells Thread-Index: AQHXjvk54dUBDCjz6UWQZn0dScb/IKtxHcpg Date: Fri, 13 Aug 2021 08:35:39 +0000 Message-ID: <0d4efdfc3b394ec2bf411dd8036c259e@AcuMS.aculab.com> References: <20210811213749.3276687-1-kuba@kernel.org> <20210811213749.3276687-4-kuba@kernel.org> In-Reply-To: <20210811213749.3276687-4-kuba@kernel.org> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Jakub Kicinski > Sent: 11 August 2021 22:38 > > skbs are freed on error and not put on the ring. We may, however, > be in a situation where we're freeing the last skb of a batch, > and there is a doorbell ring pending because of xmit_more() being > true earlier. Make sure we ring the door bell in such situations. > > Since errors are rare don't pay attention to xmit_more() and just > always flush the pending frames. > ... > +tx_free: > dev_kfree_skb_any(skb); > +tx_kick_pending: > + tx_buf->skb = NULL; > + if (txr->kick_pending) > + bnxt_txr_db_kick(bp, txr, txr->tx_prod); > return NETDEV_TX_OK; Is this case actually so unlikely that the 'kick' can be done unconditionally? Then all the conditionals can be removed from the hot path. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)