From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id B096BA04BC; Fri, 9 Oct 2020 11:40:24 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 244561C24A; Fri, 9 Oct 2020 11:40:22 +0200 (CEST) Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by dpdk.org (Postfix) with ESMTP id 29A631C241 for ; Fri, 9 Oct 2020 11:40:18 +0200 (CEST) IronPort-SDR: D0bXsz7+zleuZug5oE1lUuBE72WZy07UGQXAJo22BoT12NKsMMA6/IkhzLiwHMk4wOoUmOkV3X pxim+UskFnXg== X-IronPort-AV: E=McAfee;i="6000,8403,9768"; a="165525865" X-IronPort-AV: E=Sophos;i="5.77,354,1596524400"; d="scan'208";a="165525865" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Oct 2020 02:40:17 -0700 IronPort-SDR: 9QpBwEycxQA31s5asZP6ySKwa0NcnSvOpNNfRT9IIgGcuW7Aev1SH9nx99IRI9OaL4k4v1asTP XCs4ESUUePRg== X-IronPort-AV: E=Sophos;i="5.77,354,1596524400"; d="scan'208";a="462134168" Received: from pswirydc-mobl1.ger.corp.intel.com (HELO [10.213.3.170]) ([10.213.3.170]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Oct 2020 02:40:12 -0700 To: Thomas Monjalon Cc: Jerin Jacob , "Ananyev, Konstantin" , David Marchand , "Ma, Liang J" , dpdk-dev , "Hunt, David" , Stephen Hemminger , Honnappa Nagarahalli , "Ruifeng Wang (Arm Technology China)" , David Christensen , Jerin Jacob References: <1599214740-3927-1-git-send-email-liang.j.ma@intel.com> <3735900.a7ZSN3H2iV@thomas> From: "Burakov, Anatoly" Message-ID: <4d9bca84-a265-c87c-1200-e1981bb7e166@intel.com> Date: Fri, 9 Oct 2020 10:40:10 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <3735900.a7ZSN3H2iV@thomas> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [PATCH v4 02/10] eal: add power management intrinsics 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: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 09-Oct-20 10:29 AM, Thomas Monjalon wrote: > 09/10/2020 11:25, Burakov, Anatoly: >> On 09-Oct-20 6:42 AM, Jerin Jacob wrote: >>> On Thu, Oct 8, 2020 at 10:38 PM Ananyev, Konstantin >>> wrote: >>>> >>>>> >>>>> On Thu, Oct 8, 2020 at 6:57 PM Burakov, Anatoly >>>>> wrote: >>>>>> >>>>>> On 08-Oct-20 9:44 AM, Jerin Jacob wrote: >>>>>>> On Thu, Oct 8, 2020 at 2:04 PM Thomas Monjalon wrote: >>>>>>>> >>>>>>>>> Add two new power management intrinsics, and provide an implementation >>>>>>>>> in eal/x86 based on UMONITOR/UMWAIT instructions. The instructions >>>>>>>>> are implemented as raw byte opcodes because there is not yet widespread >>>>>>>>> compiler support for these instructions. >>>>>>>>> >>>>>>>>> The power management instructions provide an architecture-specific >>>>>>>>> function to either wait until a specified TSC timestamp is reached, or >>>>>>>>> optionally wait until either a TSC timestamp is reached or a memory >>>>>>>>> location is written to. The monitor function also provides an optional >>>>>>>>> comparison, to avoid sleeping when the expected write has already >>>>>>>>> happened, and no more writes are expected. >>>>>>>>> >>>>>>>>> For more details, Please reference Intel SDM Volume 2. >>>>>>>> >>>>>>>> I really would like to see feedbacks from other arch maintainers. >>>>>>>> Unfortunately they were not Cc'ed. >>>>>>> >>>>>>> Shared the feedback from the arm64 perspective here. Yet to get a reply on this. >>>>>>> http://mails.dpdk.org/archives/dev/2020-September/181646.html >>>>>>> >>>>>>>> Also please mark the new functions as experimental. >>>>>>>> >>>>>>>> >>>>>> >>>>>> Hi Jerin, >>>>> >>>>> Hi Anatoly, >>>>> >>>>>> >>>>>> > IMO, We must introduce some arch feature-capability _get_ scheme to tell >>>>>> > the consumer of this API is only supported on x86. Probably as >>>>>> functions[1] >>>>>> > or macro flags scheme and have a stub for the other architectures as the >>>>>> > API marked as generic ie rte_power_* not rte_x86_.. >>>>>> > >>>>>> > This will help the consumer to create workers based on the >>>>>> instruction features >>>>>> > which can NOT be abstracted as a generic feature across the >>>>>> architectures. >>>>>> >>>>>> I'm not entirely sure what you mean by that. >>>>>> >>>>>> I mean, yes, we should have added stubs for other architectures, and we >>>>>> will add those in future revisions, but what does your proposed runtime >>>>>> check accomplish that cannot currently be done with CPUID flags? >>>>> >>>>> >>>>> RTE_CPUFLAG_WAITPKG flag definition is not available in other architectures. >>>>> i.e RTE_CPUFLAG_WAITPKG defined in lib/librte_eal/x86/include/rte_cpuflags.h >>>>> and it is used in http://patches.dpdk.org/patch/79540/ as generic API. >>>>> I doubt http://patches.dpdk.org/patch/79540/ would compile on non-x86. >>>> >>>> >>>> I am agree with Jerin, that we need some generic way to >>>> figure-out does platform supports power_monitor() or not. >>>> Though not sure do we need to create a new feature-get framework here... >>> >>> That's works too. Some means of generic probing is fine. Following >>> schemed needs >>> more documentation on that usage, as, it is not straight forward compare to >>> feature-get framework. Also, on the other thread, we are adding the >>> new instructions like >>> demote cacheline etc, maybe if the user wants to KNOW if the arch >>> supports it then >>> the feature-get framework is good. >>> If we think, there is no other usecase for generic arch feature-get >>> framework then >>> we can keep the below scheme else generic arch feature is better for >>> more forward >>> looking use cases. >>> >>>> Might be just something like: >>>> rte_power_monitor(...) == -ENOTSUP >>>> be enough indication for that? >>>> So user can just do: >>>> if (rte_power_monitor(NULL, 0, 0, 0, 0) == -ENOTSUP) { >>>> /* not supported path */ >>>> } >>>> >>>> To check is that feature supported or not. >>> >>> >> >> Looking at CLDEMOTE patches, CLDEMOTE is a noop on other archs. I think >> we can safely make this intrinsic as a noop on other archs as well, as >> it's functionally identical to waking up immediately. >> >> If we're not creating this for CLDEMOTE, we don't need it here as well. >> If we do need it for this, then we arguably need it for CLDEMOTE too. > > Sorry I don't understand what you mean, too many "it" and "this" :) > Sorry, i meant "the generic feature-get framework". CLDEMOTE doesn't exist on other archs, this doesn't too, so it's a fairly similar situation. Stubbing UMWAIT with a noop is a valid approach because it's equivalent to sleeping and then immediately waking up (which can happen for a host of reasons unrelated to the code itself). I'm not against a generic feature-get framework, i'm just pointing out that if this is what's preventing the merge, it should prevent the merge of CLDEMOTE as well, yet Jerin has acked that one and has explicitly stated that he's OK with leaving CLDEMOTE as a noop on other architectures. -- Thanks, Anatoly