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 1849CA0A0C; Tue, 29 Jun 2021 13:39:56 +0200 (CEST) Received: from [217.70.189.124] (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 923A94117C; Tue, 29 Jun 2021 13:39:55 +0200 (CEST) Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by mails.dpdk.org (Postfix) with ESMTP id 4E79D40E01 for ; Tue, 29 Jun 2021 13:39:53 +0200 (CEST) X-IronPort-AV: E=McAfee;i="6200,9189,10029"; a="269260285" X-IronPort-AV: E=Sophos;i="5.83,308,1616482800"; d="scan'208";a="269260285" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jun 2021 04:39:51 -0700 X-IronPort-AV: E=Sophos;i="5.83,308,1616482800"; d="scan'208";a="625600771" Received: from aburakov-mobl.ger.corp.intel.com (HELO [10.213.252.170]) ([10.213.252.170]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jun 2021 04:39:50 -0700 To: "Ananyev, Konstantin" , "dev@dpdk.org" , "Hunt, David" Cc: "Loftus, Ciara" References: <676eab0e1eb6c63acb170893675daa5a39eac29d.1624884053.git.anatoly.burakov@intel.com> <77f30ce1-40b0-b427-c0f9-359a350358a1@intel.com> From: "Burakov, Anatoly" Message-ID: Date: Tue, 29 Jun 2021 12:39:46 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 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 v3 6/7] power: support monitoring multiple Rx queues 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 29-Jun-21 1:07 AM, Ananyev, Konstantin wrote: > > >>>> Use the new multi-monitor intrinsic to allow monitoring multiple ethdev >>>> Rx queues while entering the energy efficient power state. The multi >>>> version will be used unconditionally if supported, and the UMWAIT one >>>> will only be used when multi-monitor is not supported by the hardware. >>>> >>>> Signed-off-by: Anatoly Burakov >>>> --- >>>> doc/guides/prog_guide/power_man.rst | 9 ++-- >>>> lib/power/rte_power_pmd_mgmt.c | 76 ++++++++++++++++++++++++++++- >>>> 2 files changed, 80 insertions(+), 5 deletions(-) >>>> >>>> diff --git a/doc/guides/prog_guide/power_man.rst b/doc/guides/prog_guide/power_man.rst >>>> index fac2c19516..3245a5ebed 100644 >>>> --- a/doc/guides/prog_guide/power_man.rst >>>> +++ b/doc/guides/prog_guide/power_man.rst >>>> @@ -221,13 +221,16 @@ power saving whenever empty poll count reaches a certain number. >>>> The "monitor" mode is only supported in the following configurations and scenarios: >>>> >>>> * If ``rte_cpu_get_intrinsics_support()`` function indicates that >>>> + ``rte_power_monitor_multi()`` function is supported by the platform, then >>>> + monitoring multiple Ethernet Rx queues for traffic will be supported. >>>> + >>>> +* If ``rte_cpu_get_intrinsics_support()`` function indicates that only >>>> ``rte_power_monitor()`` is supported by the platform, then monitoring will be >>>> limited to a mapping of 1 core 1 queue (thus, each Rx queue will have to be >>>> monitored from a different lcore). >>>> >>>> -* If ``rte_cpu_get_intrinsics_support()`` function indicates that the >>>> - ``rte_power_monitor()`` function is not supported, then monitor mode will not >>>> - be supported. >>>> +* If ``rte_cpu_get_intrinsics_support()`` function indicates that neither of the >>>> + two monitoring functions are supported, then monitor mode will not be supported. >>>> >>>> * Not all Ethernet devices support monitoring, even if the underlying >>>> platform may support the necessary CPU instructions. Please refer to >>>> diff --git a/lib/power/rte_power_pmd_mgmt.c b/lib/power/rte_power_pmd_mgmt.c >>>> index 7762cd39b8..aab2d4f1ee 100644 >>>> --- a/lib/power/rte_power_pmd_mgmt.c >>>> +++ b/lib/power/rte_power_pmd_mgmt.c >>>> @@ -155,6 +155,24 @@ queue_list_remove(struct pmd_core_cfg *cfg, const union queue *q) >>>> return 0; >>>> } >>>> >>>> +static inline int >>>> +get_monitor_addresses(struct pmd_core_cfg *cfg, >>>> + struct rte_power_monitor_cond *pmc) >>>> +{ >>>> + const struct queue_list_entry *qle; >>>> + size_t i = 0; >>>> + int ret; >>>> + >>>> + TAILQ_FOREACH(qle, &cfg->head, next) { >>>> + struct rte_power_monitor_cond *cur = &pmc[i]; >>> >>> Looks like you never increment 'i' value inside that function. >>> Also it probably will be safer to add 'num' parameter to check that >>> we will never over-run pmc[] boundaries. >> >> Will fix in v4, good catch! >> >>> >>>> + const union queue *q = &qle->queue; >>>> + ret = rte_eth_get_monitor_addr(q->portid, q->qid, cur); >>>> + if (ret < 0) >>>> + return ret; >>>> + } >>>> + return 0; >>>> +} >>>> + >>>> static void >>>> calc_tsc(void) >>>> { >>>> @@ -183,6 +201,48 @@ calc_tsc(void) >>>> } >>>> } >>>> >>>> +static uint16_t >>>> +clb_multiwait(uint16_t port_id, uint16_t qidx, >>>> + struct rte_mbuf **pkts __rte_unused, uint16_t nb_rx, >>>> + uint16_t max_pkts __rte_unused, void *addr __rte_unused) >>>> +{ >>>> + const unsigned int lcore = rte_lcore_id(); >>>> + const union queue q = {.portid = port_id, .qid = qidx}; >>>> + const bool empty = nb_rx == 0; >>>> + struct pmd_core_cfg *q_conf; >>>> + >>>> + q_conf = &lcore_cfg[lcore]; >>>> + >>>> + /* early exit */ >>>> + if (likely(!empty)) { >>>> + q_conf->empty_poll_stats = 0; >>>> + } else { >>>> + /* do we care about this particular queue? */ >>>> + if (!queue_is_power_save(q_conf, &q)) >>>> + return nb_rx; >>> >>> I still don't understand the need of 'special' power_save queue here... >>> Why we can't just have a function: >>> >>> get_number_of_queues_whose_sequential_empty_polls_less_then_threshold(struct pmd_core_cfg *lcore_cfg), >>> and then just: >>> >>> /* all queues have at least EMPTYPOLL_MAX sequential empty polls */ >>> if (get_number_of_queues_whose_sequential_empty_polls_less_then_threshold(q_conf) == 0) { >>> /* go into power-save mode here */ >>> } >> >> Okay, let's go through this step by step :) >> >> Let's suppose we have three queues - q0, q1 and q2. We want to sleep >> whenever there's no traffic on *all of them*, however we cannot know >> that until we have checked all of them. >> >> So, let's suppose that q0, q1 and q2 were empty all this time, but now >> some traffic arrived at q2 while we're still checking q0. We see that q0 >> is empty, and all of the queues were empty for the last N polls, so we >> think we will be safe to sleep at q0 despite the fact that traffic has >> just arrived at q2. >> This is not an issue with MONITOR mode because we will be able to see if >> current Rx ring descriptor is busy or not via the NIC callback, *but >> this is not possible* with PAUSE and SCALE modes, because they don't >> have the sneaky lookahead function of MONITOR! So, with PAUSE and SCALE >> modes, it is possible to end up in a situation where you *think* you >> don't have any traffic, but you actually do, you just haven't checked >> the relevant queue yet. > > I think such situation is unavoidable. > Yes, traffic can arrive to *any* queue at *any* time. > With your example above - user choose q2 as 'special' queue, but > traffic actually arrives on q0 or q1. > And yes, if user choose PAUSE or SCALE methods he *can* miss the traffic, > because as you said for these methods there is no notification mechanisms. > I think there are just unavoidable limitations with these power-save methods. > >> In order to prevent this from happening, we do not sleep on every queue, >> instead we sleep *once* per loop. > > Yes, totally agree we shouldn't sleep on *every* queue. > We need to go to sleep when there is no traffic on *any* of queues we monitor. > >> That is, we check q0, check q1, check >> q2, and only then we decide whether we want to sleep or not. > >> Of course, with such scheme it is still possible to e.g. sleep in q2 >> while there's traffic waiting in q0, > > Yes, exactly. > >> but worst case is less bad with >> this scheme, because we'll be doing at worst 1 extra sleep. > > Hmm, I think it would be one extra sleep anyway. > >> Whereas with what you're suggesting, if we had e.g. 10 queues to poll, >> and we checked q1 but traffic has just arrived at q0, we'll be sleeping >> at q1, then we'll be sleeping at q2, then we'll be sleeping at q3, then >> we'll be sleeping at q4, then we'll be sleeping at q5.... and 9 sleeps >> later we finally reach q0 and find out after all this time that we >> shouldn't have slept in the first place. > > Ah ok, I think I understand now what you are saying. > Sure, to avoid such situation, we'll need to maintain extra counters and > update them properly when we go to sleep. > I should state it clearly at the beginning. > It might be easier to explain what I meant by code snippet: > > lcore_conf needs 2 counters: > uint64_t nb_queues_ready_to_sleep; > uint64_t nb_sleeps; > > Plus each queue needs 2 counters: > uint64_t nb_empty_polls; > uint64_t nb_sleeps; > > Now, at rx_callback(): > > /* check did sleep happen since previous call, > if yes, then reset queue counters */ > if (queue->nb_sleeps != lcore_conf->nb_sleeps) { > queue->nb_sleeps = lcore_conf->nb_sleeps; > queue->nb_empty_polls = 0; > } > > /* packet arrived, reset counters */ > if (nb_rx != 0) { > /* queue is not 'ready_to_sleep' any more */ > if (queue->nb_empty_polls > EMPTYPOLL_MAX) > lcore_conf-> nb_queues_ready_to_sleep--; > queue->nb_empty_polls = 0; > > /* empty poll */ > } else { > /* queue reaches EMPTYPOLL_MAX threshold, mark it as 'ready_to_sleep' */ > if (queue->nb_empty_polls == EMPTYPOLL_MAX) > lcore_conf-> nb_queues_ready_to_sleep++; > queue->nb_empty_polls++; > } > > /* no traffic on any queue for at least EMPTYPOLL_MAX iterations */ > if (lcore_conf-> nb_queues_ready_to_sleep == lcore_conf->n_queues) { > /* update counters and sleep */ > lcore_conf->nb_sleeps++; > lcore_conf-> nb_queues_ready_to_sleep = 0; > goto_sleep(); > } > } > Actually, i don't think this is going to work, because i can see no (easy) way to get from lcore to specific queue. I mean, you could have an O(N) for loop that will loop over the list of queues every time we enter the callback, but i don't think that's such a good idea. -- Thanks, Anatoly