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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00725C77B72 for ; Thu, 20 Apr 2023 18:51:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231261AbjDTSvM (ORCPT ); Thu, 20 Apr 2023 14:51:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55976 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230118AbjDTSvL (ORCPT ); Thu, 20 Apr 2023 14:51:11 -0400 Received: from mx04lb.world4you.com (mx04lb.world4you.com [81.19.149.114]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62FDF2705; Thu, 20 Apr 2023 11:51:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=engleder-embedded.com; s=dkim11; h=Content-Transfer-Encoding:Content-Type: In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=nicpazsYFo+cOS55Zsy7iQP/8Rjk32Z/JcO9Q8jUJvQ=; b=Q3Ta1HVcX48cTOHeqzciD0Vz+J z4YT4VMxJBj2qjD/LklWZ7wyuBCXSh539AEk8qw/UobK4D74susDMRfkmze+4fykP83Ao9zQCCjuP byVw22Zjv4KfoJA2RTt/wmp5X3OeRzl59cRzkxWu9T5dJVYN8f1XHlBHK93A3Nc4IoOE=; Received: from [88.117.57.231] (helo=[10.0.0.160]) by mx04lb.world4you.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1ppZN5-0005lM-J1; Thu, 20 Apr 2023 20:51:07 +0200 Message-ID: <7dcca571-856b-36f9-cf56-4a3c63c07e4e@engleder-embedded.com> Date: Thu, 20 Apr 2023 20:51:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH net-next v3 1/6] tsnep: Replace modulo operation with mask Content-Language: en-US To: Stephen Hemminger , Maciej Fijalkowski Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, davem@davemloft.net, kuba@kernel.org, edumazet@google.com, pabeni@redhat.com, bjorn@kernel.org, magnus.karlsson@intel.com, jonathan.lemon@gmail.com References: <20230418190459.19326-1-gerhard@engleder-embedded.com> <20230418190459.19326-2-gerhard@engleder-embedded.com> <20230420081013.6e2040c5@hermes.local> From: Gerhard Engleder In-Reply-To: <20230420081013.6e2040c5@hermes.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-AV-Do-Run: Yes Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 20.04.23 17:10, Stephen Hemminger wrote: > On Thu, 20 Apr 2023 16:23:10 +0200 > Maciej Fijalkowski wrote: > >> On Tue, Apr 18, 2023 at 09:04:54PM +0200, Gerhard Engleder wrote: >>> TX/RX ring size is static and power of 2 to enable compiler to optimize >>> modulo operation to mask operation. Make this optimization already in >>> the code and don't rely on the compiler. >> >> I think this came out of my review, so: >> Suggested-by: Maciej Fijalkowski >> >> Does this give you a minor perf boost? > > If you change the loop counter to be unsigned, then Gcc (and Clang) > will optimize this into a mask operation. That is a better simpler fix. > > If loop counter (i) is an integer, then compiler has keep the > potential for wrap around. I'm unsure which solution should be preferred. But I could change to unsigned anyway.