From patchwork Thu Dec 19 12:39:21 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Magnus Karlsson X-Patchwork-Id: 1213309 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: incoming-bpf@patchwork.ozlabs.org Delivered-To: patchwork-incoming-bpf@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=bpf-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=intel.com Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 47ds000Q1Pz9sPn for ; Thu, 19 Dec 2019 23:39:44 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726734AbfLSMjn (ORCPT ); Thu, 19 Dec 2019 07:39:43 -0500 Received: from mga11.intel.com ([192.55.52.93]:27930 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726695AbfLSMjn (ORCPT ); Thu, 19 Dec 2019 07:39:43 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Dec 2019 04:39:43 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,331,1571727600"; d="scan'208";a="366062500" Received: from mkarlsso-mobl.ger.corp.intel.com (HELO localhost.localdomain) ([10.252.49.245]) by orsmga004.jf.intel.com with ESMTP; 19 Dec 2019 04:39:40 -0800 From: Magnus Karlsson To: magnus.karlsson@intel.com, bjorn.topel@intel.com, ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org, jonathan.lemon@gmail.com Cc: bpf@vger.kernel.org, saeedm@mellanox.com, jeffrey.t.kirsher@intel.com, maciej.fijalkowski@intel.com, maciejromanfijalkowski@gmail.com Subject: [PATCH bpf-next v2 02/12] xsk: simplify detection of empty and full rings Date: Thu, 19 Dec 2019 13:39:21 +0100 Message-Id: <1576759171-28550-3-git-send-email-magnus.karlsson@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1576759171-28550-1-git-send-email-magnus.karlsson@intel.com> References: <1576759171-28550-1-git-send-email-magnus.karlsson@intel.com> Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org In order to set the correct return flags for poll, the xsk code has to check if the Rx queue is empty and if the Tx queue is full. This code was unnecessarily large and complex as it used the functions that are used to update the local state from the global state (xskq_nb_free and xskq_nb_avail). Since we are not doing this nor updating any data dependent on this state, we can simplify the functions. Another benefit from this is that we can also simplify the xskq_nb_free and xskq_nb_avail functions in a later commit. Signed-off-by: Magnus Karlsson --- net/xdp/xsk_queue.h | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h index a2f0ba6..b28f9da 100644 --- a/net/xdp/xsk_queue.h +++ b/net/xdp/xsk_queue.h @@ -362,12 +362,15 @@ static inline void xskq_produce_flush_desc(struct xsk_queue *q) static inline bool xskq_full_desc(struct xsk_queue *q) { - return xskq_nb_avail(q, q->nentries) == q->nentries; + /* No barriers needed since data is not accessed */ + return READ_ONCE(q->ring->producer) - READ_ONCE(q->ring->consumer) == + q->nentries; } static inline bool xskq_empty_desc(struct xsk_queue *q) { - return xskq_nb_free(q, q->prod_tail, q->nentries) == q->nentries; + /* No barriers needed since data is not accessed */ + return READ_ONCE(q->ring->consumer) == READ_ONCE(q->ring->producer); } void xskq_set_umem(struct xsk_queue *q, u64 size, u64 chunk_mask);