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 588C5A04BC; Fri, 9 Oct 2020 12:03:27 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 58C191C2AA; Fri, 9 Oct 2020 12:03:25 +0200 (CEST) Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by dpdk.org (Postfix) with ESMTP id 907B41C235 for ; Fri, 9 Oct 2020 12:03:23 +0200 (CEST) IronPort-SDR: iII8G2B9FKtMN6vvBw0c+sLMOT3Vyv0G08ZsdPupebZ9y2soc1l807aqpv1behVGJngi9CuZiU lzbhnJp/Dopw== X-IronPort-AV: E=McAfee;i="6000,8403,9768"; a="182905435" X-IronPort-AV: E=Sophos;i="5.77,354,1596524400"; d="scan'208";a="182905435" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Oct 2020 03:03:21 -0700 IronPort-SDR: R/FsLmDPCPjnasQ3n6sgIbwM2NkwqwTImXxd4MSu0RSwerJXkSpeGPufSzsU+FlPssKj5j+6+l K7oGBtRer8kA== X-IronPort-AV: E=Sophos;i="5.77,354,1596524400"; d="scan'208";a="462139799" Received: from aburakov-mobl.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 03:03:17 -0700 To: Jerin Jacob Cc: Thomas Monjalon , "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> <4d9bca84-a265-c87c-1200-e1981bb7e166@intel.com> From: "Burakov, Anatoly" Message-ID: <92b20fa1-f37a-9938-90a7-72956a206b62@intel.com> Date: Fri, 9 Oct 2020 11:03:14 +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: 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 10:54 AM, Jerin Jacob wrote: > On Fri, Oct 9, 2020 at 3:10 PM Burakov, Anatoly > wrote: >> >> 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). > > If we are keeping the following return in the public API then it can not be NOP > + * @return > + * - 1 if wakeup was due to TSC timeout expiration. > + * - 0 if wakeup was due to memory write or other reasons. > + */ > In the generic header, it is specified that return value is implementation-defined (i.e. arch-specific). I guess we could remove that and set return value to either 0 or -ENOTSUP if that would resolve the issue? > Also, we need to fix compilation issue if any with > http://patches.dpdk.org/patch/79540/ > as it has direct reference to if > (!rte_cpu_get_flag_enabled(RTE_CPUFLAG_WAITPKG)) { > Either we need to add -ENOTSUP return or generic feature-get framework. IIRC power library isn't compiled on anything other than x86, so this code wouldn't get compiled. > > >> >> 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 -- Thanks, Anatoly