From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f52.google.com (mail-wm0-f52.google.com [74.125.82.52]) by dpdk.org (Postfix) with ESMTP id 1809F2949 for ; Wed, 9 Mar 2016 16:28:11 +0100 (CET) Received: by mail-wm0-f52.google.com with SMTP id n186so184169153wmn.1 for ; Wed, 09 Mar 2016 07:28:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=6wind-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:organization:user-agent :in-reply-to:references:mime-version:content-transfer-encoding; bh=+1WMK2lgCJ3xbWTg4oIgcZTHePQZNk8SMXnCfobatFQ=; b=pzMRHKhHUNxObGK2h6IBxpcI7mUJt+PSx5sOvRIuq5fO+A3ba0do2tdZnrS7PCNIyS OR1ILwb3aa9N+o5Z2w1lHbgmUKoUYbxHeXzA0/nej7OoJsMmzY0UYgrqNeLt4hsACTMS 1kxxJeQ3oTAc9qcG2b5AJX0GdN0W0RJxgeLpJZ05CMoAqlqOP5wj/tPtt24zopKEtZy7 vSTW/rvQtsV0rPDQWEbIWf8EX/Zpy/G7IL07BnpcbJRmmaVq63O8lhy/PoQ1DRaUeO4y d/+5villu4KRtZ0K88WH5y2NzBNeBicjmLHtYiCprLAp6o5w9gCVmZGnSDb461twomI7 vcTg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:organization :user-agent:in-reply-to:references:mime-version :content-transfer-encoding; bh=+1WMK2lgCJ3xbWTg4oIgcZTHePQZNk8SMXnCfobatFQ=; b=ewOs226XZAUXeR3FvfaKo7Ov1FWTBZyQRCc3OaCwyaeWuGXK0oC1oVSzdQ7y+pOQbo /2NOFGCbHczkReldGc33eI58qFfu1bVdDxkBORkpzUDVOg6eDHsspOBquXALuIacsmNR oQXUDAZkpp2ij3/gNDFw8/DWNDq4DGCCY8dGWfYnpVSaqg7wnlWkuXZxsVSeX+CMhacw RFHPstac51xdw31vRNHL24egxBiaU44p1wS6CxOwvTBepL6sUTNyTaZSuxEynADpFDZK +Cr2o51l6p/JMrpTt37Yd3n8E18iPohpcHPagPBBlxpczxKwvBQ3i5JOVWCa3Ik+pCX/ 2h4Q== X-Gm-Message-State: AD7BkJILeRUgIv6nSdb4EfynKGgJZOEGGpUVF8LTpDhJ9mfUIRd4v8Pi3Og/fBgIlA2FBNW/ X-Received: by 10.194.113.38 with SMTP id iv6mr35608020wjb.126.1457537290969; Wed, 09 Mar 2016 07:28:10 -0800 (PST) Received: from xps13.localnet (171.36.101.84.rev.sfr.net. [84.101.36.171]) by smtp.gmail.com with ESMTPSA id j18sm24531053wmd.2.2016.03.09.07.28.09 (version=TLSv1/SSLv3 cipher=OTHER); Wed, 09 Mar 2016 07:28:10 -0800 (PST) From: Thomas Monjalon To: "Ananyev, Konstantin" Date: Wed, 09 Mar 2016 16:26:30 +0100 Message-ID: <5916803.8PiAMBcxJt@xps13> Organization: 6WIND User-Agent: KMail/4.14.10 (Linux/4.1.6-1-ARCH; KDE/4.14.11; x86_64; ; ) In-Reply-To: <2601191342CEEE43887BDE71AB97725836B1A627@irsmsx105.ger.corp.intel.com> References: <1452869038-9140-1-git-send-email-tomaszx.kulasek@intel.com> <1964417.t7N6HDkJH0@xps13> <2601191342CEEE43887BDE71AB97725836B1A627@irsmsx105.ger.corp.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Cc: dev@dpdk.org Subject: Re: [dpdk-dev] [PATCH v2 1/2] ethdev: add buffered tx api X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 09 Mar 2016 15:28:11 -0000 2016-03-09 15:23, Ananyev, Konstantin: > > > > 2016-03-09 13:36, Ananyev, Konstantin: > > > > > + if (to_send == 0) > > > > > + return 0; > > > > > > > > Why this check is done in the lib? > > > > What is the performance gain if we are idle? > > > > It can be done outside if needed. > > > > > > Yes, that could be done outside, but if user has to do it anyway, > > > why not to put it inside? > > > I don't expect any performance gain/loss because of that - > > > just seems a bit more convenient to the user. > > > > It is handling an idle case so there is no gain obviously. > > But the condition branching is surely a loss. > > I suppose that condition should always be checked: > either in user code prior to function call or inside the > function call itself. > So don't expect any difference in performance here... > Do you have any particular example when you think it would? > Or are you talking about rte_eth_tx_buffer() calling > rte_eth_tx_buffer_flush() internally? > For that one - both are flush is 'static inline' , so I expect > compiler be smart enough to remove this redundant check. > > > So why the user would you like to do this check? > Just for user convenience - to save him doing that manually. Probably I've missed something. If we remove this check, the function will do nothing, right? How is it changing the behaviour?