From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 79646A0A0A; Wed, 28 Apr 2021 19:17:20 +0200 (CEST) Received: from [217.70.189.124] (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id E8E1C40697; Wed, 28 Apr 2021 19:17:19 +0200 (CEST) Received: from mail-pj1-f53.google.com (mail-pj1-f53.google.com [209.85.216.53]) by mails.dpdk.org (Postfix) with ESMTP id 396B940147 for ; Wed, 28 Apr 2021 19:17:19 +0200 (CEST) Received: by mail-pj1-f53.google.com with SMTP id lr7so15014244pjb.2 for ; Wed, 28 Apr 2021 10:17:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=vPjNr/LoWuP9X0FC9/5MIm/khO0qAeU0DoPAsB1O0s4=; b=A2XNpYMwM3EVRYm0adEQMZjjsQJ3UCQokZrU/7E2wKnhxk/W/YTHvG71xzXq7r37Dj 1R6B1CcPDAt6R2eaRSR1ropc/n3XXMNG0QHUD+twJbnhca3mbr6LYdU/IcT/Y2SSjWtc BXsVHsmpwGhKVqtFGj1yxkAJLruPQNeDJBRyizNZR4IemcIzptLWF0BP3yzzawrW51Iv LA2+dj5QFBYVXNHdiKSz5kvqnY56bYmIKRtWDU1+g6uQIwumq2qnRyxILx2rjtAH9kUk GlO+o68JRB3IyhU5ZcthxOUQZG+ZN/EkZ9juT9Oc8aS9wCPNTRavFv5V5xOWIpwXGxLp PeWg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=vPjNr/LoWuP9X0FC9/5MIm/khO0qAeU0DoPAsB1O0s4=; b=TDbz/qLzDGFbsgkenHGHpquckZw0MeU9rt9oeaGij0rkNYT6e84v76EKiTGVDdQ3m7 HvPDoTOfqcRxJEigzgb4SP9t+qY9qZV/WnE49EGIfy90A39xUDYlaUzcJtjvGUzYITY8 KM4QyBTQMfJvUOEfDdxjfEHKrAZCya+j96ZQSXlBPkA26MVgnsqyHCVLoUCWI8juGqVv Tn26iCa6aqpoDiG2naMFSal4pZOmJ2WW18RwS+5wxjLDZHRyxzYKbTGfG0SBk3THM7W9 b6S8DcPDPIuCAM75hb9hR7l5vgYyvf/eCc5lpSOoAzqYoipSO2yjs0+99Tc8VPkLIw0E o0ng== X-Gm-Message-State: AOAM5330wB67KN1sgZYhL+ObWnT5GzhVSG1+wvhZMCg1fewm7Zf26vKv 4S1NRZroG5Hc0xXMLq2vCElEkw== X-Google-Smtp-Source: ABdhPJz7L3gweZIP9ILR8qQ/7cj7gowjf+ucUgDHF9Gvjll1I3J59qAELROGg6LBuQlr/U4B+/xzcQ== X-Received: by 2002:a17:90a:a00e:: with SMTP id q14mr5224840pjp.70.1619630238186; Wed, 28 Apr 2021 10:17:18 -0700 (PDT) Received: from hermes.local (76-14-218-44.or.wavecable.com. [76.14.218.44]) by smtp.gmail.com with ESMTPSA id r32sm267380pgm.49.2021.04.28.10.17.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Apr 2021 10:17:17 -0700 (PDT) Date: Wed, 28 Apr 2021 10:17:14 -0700 From: Stephen Hemminger To: Ruifeng Wang Cc: Honnappa Nagarahalli , Konstantin Ananyev , dev@dpdk.org, david.marchand@redhat.com, thomas@monjalon.net, jerinj@marvell.com, nd@arm.com, Gavin Hu , Steve Capper , Ola Liljedahl Message-ID: <20210428101714.2e5da560@hermes.local> In-Reply-To: <20210425055653.1509261-3-ruifeng.wang@arm.com> References: <20200424070741.16619-1-gavin.hu@arm.com> <20210425055653.1509261-1-ruifeng.wang@arm.com> <20210425055653.1509261-3-ruifeng.wang@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [PATCH v3 2/2] ring: use wfe to wait for ring tail update on aarch64 X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Sun, 25 Apr 2021 05:56:53 +0000 Ruifeng Wang wrote: > Instead of polling for tail to be updated, use wfe instruction. > > Signed-off-by: Gavin Hu > Signed-off-by: Ruifeng Wang > Reviewed-by: Steve Capper > Reviewed-by: Ola Liljedahl > Reviewed-by: Honnappa Nagarahalli > Acked-by: Konstantin Ananyev Looks ok to me, but it does raise an interesting question. Shouldn't the original code have been using atomic load to look at ht->tail. This another place where "volatile considered harmful" applies.