From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out1-smtp.messagingengine.com (out1-smtp.messagingengine.com [66.111.4.25]) by dpdk.org (Postfix) with ESMTP id 3C94E201 for ; Wed, 11 Oct 2017 21:25:59 +0200 (CEST) Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailout.nyi.internal (Postfix) with ESMTP id 9889720D60; Wed, 11 Oct 2017 15:25:59 -0400 (EDT) Received: from frontend2 ([10.202.2.161]) by compute1.internal (MEProxy); Wed, 11 Oct 2017 15:25:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=monjalon.net; h= cc:content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-sender :x-me-sender:x-sasl-enc; s=mesmtp; bh=hStarDcWjgJxTI1AKF19RemdKj dI5C2OBEYVKSqSdOQ=; b=UF+QbhVbbg1Eta9AM9pNLXrmuY4nrDqyOuwApwwnN1 4H6n6yIe4sU81FKIs0Nd2cQM50oX5HYYDr8XvqDY8m5d94xkttPeCHJ8LooU1uCX 5G07KgiAUTrHxyzP0UHsEHniIh6xrRvsGT8eFq3X1geqilaqSh1bgBW8XY2kZDcZ I= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-me-sender:x-me-sender:x-sasl-enc; s=fm1; bh=hStarD cWjgJxTI1AKF19RemdKjdI5C2OBEYVKSqSdOQ=; b=KuH7HDs9MZJTS2F1hIUM8J hRrAo99Grp63gAxKYomGPiF+cbDCY4spOyVL4iKvu5xg/xzFbpVX5SYD1sPQuxJr vnofJYm+RN81Gfo7CH+ZjQcmeo7L46fhzEZKzcfuktlxziPZSJH2TIbufW3DHA9o 0iFnigam8RLIeCArKZhNNwijPzu18zoUUzTaHkzboRZZqy4ssPnhVeVdcBlqc7Dm /ViqhLnTTGXjZf+VlnI8QQftrkzbp+G4ERM7dMIsRvjsWZC+hcm1/46lcuS8QWOx ih2kEQZfjpaXxxIZPaHhlWLdMxeucTCb/Hy0mjxg6rK4Or3WgwkqwIv7MclLFqaw == X-ME-Sender: Received: from xps.localnet (184.203.134.77.rev.sfr.net [77.134.203.184]) by mail.messagingengine.com (Postfix) with ESMTPA id 37D27246D5; Wed, 11 Oct 2017 15:25:59 -0400 (EDT) From: Thomas Monjalon To: Jerin Jacob Cc: Gowrishankar , dev@dpdk.org, Chao Zhu , Bruce Richardson , Konstantin Ananyev , viktorin@rehivetech.com, jianbo.liu@linaro.org Date: Wed, 11 Oct 2017 21:25:58 +0200 Message-ID: <1897496.fbWrZq1zZe@xps> In-Reply-To: <20171011185719.GA19065@jerin> References: <3939224.L4DEiYxvN2@xps> <20171011185719.GA19065@jerin> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Subject: Re: [dpdk-dev] [PATCH v2 5/5] eal/timer: honor architecture specific rdtsc hz function X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 11 Oct 2017 19:26:00 -0000 11/10/2017 20:57, Jerin Jacob: > From: Thomas Monjalon > > 22/09/2017 10:25, Gowrishankar: > > > From: Jerin Jacob > > > > > > When calibrating the tsc frequency, first, probe the architecture specific > > > rdtsc hz function. if not available, use the existing calibrate scheme > > > to calibrate the tsc frequency. > > > > > > Signed-off-by: Jerin Jacob > > > > I agree on the idea. > > OK > > > The namespace of cycles related function in DPDK is a real mess. > > Absolutely!! > > > I think we can choose better names in this series as a first step > > to tidy this mess. > > I will explain below. > > > > At first, we should avoid TSC and RDTSC which are Intel-only wording. > > The generic word could be "cycles" (the word used in arch headers), > > or "ticks". > > We should also name the timer sources or their function in a generic way. > > Examples: CPU cycles? fast counter? precise counter? > > > > Sometimes we use "hz", sometimes "freq". > > It would better to keep one of them. > > > > > --- a/lib/librte_eal/common/eal_common_timer.c > > > +++ b/lib/librte_eal/common/eal_common_timer.c > > > @@ -80,8 +80,11 @@ > > > void > > > set_tsc_freq(void) > > > { > > > - uint64_t freq = get_tsc_freq(); > > > + uint64_t freq; > > > > > > + freq = rte_rdtsc_arch_hz(); > > > > This new function is arch-specific and exported as a new API. > > I thought of avoid exporting it. But then if the function is in > lib/librte_eal/common/include/arch/../rte_cycles.h it is anyway exposed to > application. i.e whatever files in lib/librte_eal/common/include/arch/../ > anyway exposed to application. Ah yes, you are right! > See last comment. > > > > > > + if (!freq) > > > + freq = get_tsc_freq(); > > > > The function get_tsc_freq is guessing the freq with OS-specific method. > > > > > if (!freq) > > > freq = estimate_tsc_freq(); > > > > The function estimate_tsc_freq is doing an estimation based on sleep(). > > > > At the end, the most accurate frequency is saved in eal_tsc_resolution_hz > > and can be retrieved with rte_get_tsc_hz(). > > I don't understand why rte_rdtsc_arch_hz() is also exported to the apps. > > > > TSC and HPET timer sources are wrapped in rte_get_timer_hz() in the > > Similarly we can get the current timer with rte_get_timer_cycles(). > > In the case of TSC, it calls rte_get_tsc_cycles() which is an alias > > of rte_rdtsc(). > > Some code is still using directly rte_rdtsc(). > > There is also rte_rdtsc_precise which adds a memory barrier. > > > > The real question is what is the right abstraction for the application? > > Do we want the fastest timer? the CPU timer? a precise timer? > > > > I would like to see a real discussion on this topic, in order of building > > a new timer API which would alias the old one for some time. > > I guess, we may need to see to how abstract vmware TSC support also in > proper way Yes > > If you don't want to bother with all these questions, I suggest to not > > export the new function rte_rdtsc_arch_hz() and rename it to tsc_arch_hz. > > If I understand it correctly, You would like to create a header file > in lib/librte_eal/common/include/arch/../ which should not be exported and change > the name to tsc_arch_hz. I had not think about the way to do this. What about having internal headers in lib/librte_eal/common/arch/ ?