From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D490C31E59 for ; Mon, 17 Jun 2019 10:00:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4FBD720833 for ; Mon, 17 Jun 2019 10:00:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727998AbfFQKAv (ORCPT ); Mon, 17 Jun 2019 06:00:51 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:52296 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727518AbfFQKAu (ORCPT ); Mon, 17 Jun 2019 06:00:50 -0400 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x5H9xjmT027721 for ; Mon, 17 Jun 2019 06:00:49 -0400 Received: from e06smtp01.uk.ibm.com (e06smtp01.uk.ibm.com [195.75.94.97]) by mx0b-001b2d01.pphosted.com with ESMTP id 2t66nbn3cj-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 17 Jun 2019 06:00:47 -0400 Received: from localhost by e06smtp01.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 17 Jun 2019 11:00:45 +0100 Received: from b06cxnps3074.portsmouth.uk.ibm.com (9.149.109.194) by e06smtp01.uk.ibm.com (192.168.101.131) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 17 Jun 2019 11:00:40 +0100 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x5HA0dQj54853752 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 17 Jun 2019 10:00:39 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AE041A406B; Mon, 17 Jun 2019 10:00:39 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3EABBA4051; Mon, 17 Jun 2019 10:00:38 +0000 (GMT) Received: from boston16h.aus.stglabs.ibm.com (unknown [9.3.23.78]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 17 Jun 2019 10:00:38 +0000 (GMT) From: Abhishek Goel To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-pm@vger.kernel.org Cc: rjw@rjwysocki.net, daniel.lezcano@linaro.org, mpe@ellerman.id.au, dja@axtens.net, npiggin@gmail.com, ego@linux.vnet.ibm.com, Abhishek Goel Subject: [PATCH v2 1/1] cpuidle-powernv : forced wakeup for stop states Date: Mon, 17 Jun 2019 04:56:48 -0500 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190617095648.18847-1-huntbag@linux.vnet.ibm.com> References: <20190617095648.18847-1-huntbag@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 19061710-4275-0000-0000-00000342FDA9 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19061710-4276-0000-0000-000038531FEB Message-Id: <20190617095648.18847-2-huntbag@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-17_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906170093 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Currently, the cpuidle governors determine what idle state a idling CPU should enter into based on heuristics that depend on the idle history on that CPU. Given that no predictive heuristic is perfect, there are cases where the governor predicts a shallow idle state, hoping that the CPU will be busy soon. However, if no new workload is scheduled on that CPU in the near future, the CPU may end up in the shallow state. This is problematic, when the predicted state in the aforementioned scenario is a shallow stop state on a tickless system. As we might get stuck into shallow states for hours, in absence of ticks or interrupts. To address this, We forcefully wakeup the cpu by setting the decrementer. The decrementer is set to a value that corresponds with the residency of the next available state. Thus firing up a timer that will forcefully wakeup the cpu. Few such iterations will essentially train the governor to select a deeper state for that cpu, as the timer here corresponds to the next available cpuidle state residency. Thus, cpu will eventually end up in the deepest possible state. Signed-off-by: Abhishek Goel --- Auto-promotion v1 : started as auto promotion logic for cpuidle states in generic driver v2 : Removed timeout_needed and rebased the code to upstream kernel Forced-wakeup v1 : New patch with name of forced wakeup started v2 : Extending the forced wakeup logic for all states. Setting the decrementer instead of queuing up a hrtimer to implement the logic. drivers/cpuidle/cpuidle-powernv.c | 38 +++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c index 84b1ebe212b3..bc9ca18ae7e3 100644 --- a/drivers/cpuidle/cpuidle-powernv.c +++ b/drivers/cpuidle/cpuidle-powernv.c @@ -46,6 +46,26 @@ static struct stop_psscr_table stop_psscr_table[CPUIDLE_STATE_MAX] __read_mostly static u64 default_snooze_timeout __read_mostly; static bool snooze_timeout_en __read_mostly; +static u64 forced_wakeup_timeout(struct cpuidle_device *dev, + struct cpuidle_driver *drv, + int index) +{ + int i; + + for (i = index + 1; i < drv->state_count; i++) { + struct cpuidle_state *s = &drv->states[i]; + struct cpuidle_state_usage *su = &dev->states_usage[i]; + + if (s->disabled || su->disable) + continue; + + return (s->target_residency + 2 * s->exit_latency) * + tb_ticks_per_usec; + } + + return 0; +} + static u64 get_snooze_timeout(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) @@ -144,8 +164,26 @@ static int stop_loop(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { + u64 dec_expiry_tb, dec, timeout_tb, forced_wakeup; + + dec = mfspr(SPRN_DEC); + timeout_tb = forced_wakeup_timeout(dev, drv, index); + forced_wakeup = 0; + + if (timeout_tb && timeout_tb < dec) { + forced_wakeup = 1; + dec_expiry_tb = mftb() + dec; + } + + if (forced_wakeup) + mtspr(SPRN_DEC, timeout_tb); + power9_idle_type(stop_psscr_table[index].val, stop_psscr_table[index].mask); + + if (forced_wakeup) + mtspr(SPRN_DEC, dec_expiry_tb - mftb()); + return index; } -- 2.17.1