From patchwork Fri Jul 12 07:04:55 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Abhishek Goel X-Patchwork-Id: 1131178 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 45lPGP0q1cz9s7T for ; Fri, 12 Jul 2019 17:10:53 +1000 (AEST) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.vnet.ibm.com Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 45lPGN6R2bzDqC8 for ; Fri, 12 Jul 2019 17:10:52 +1000 (AEST) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=none (mailfrom) smtp.mailfrom=linux.vnet.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=huntbag@linux.vnet.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.vnet.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 45lP8L33HrzDqs1 for ; Fri, 12 Jul 2019 17:05:38 +1000 (AEST) Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x6C74afA125947 for ; Fri, 12 Jul 2019 03:05:36 -0400 Received: from e06smtp01.uk.ibm.com (e06smtp01.uk.ibm.com [195.75.94.97]) by mx0a-001b2d01.pphosted.com with ESMTP id 2tpngg81d6-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 12 Jul 2019 03:05:36 -0400 Received: from localhost by e06smtp01.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 12 Jul 2019 08:05:34 +0100 Received: from b06cxnps4076.portsmouth.uk.ibm.com (9.149.109.198) 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) Fri, 12 Jul 2019 08:05:31 +0100 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x6C75UQq51314826 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 12 Jul 2019 07:05:30 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0A92652051; Fri, 12 Jul 2019 07:05:30 +0000 (GMT) Received: from boston16h.aus.stglabs.ibm.com (unknown [9.3.23.78]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 892795204F; Fri, 12 Jul 2019 07:05:28 +0000 (GMT) From: Abhishek Goel To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-pm@vger.kernel.org Subject: [PATCH v4 1/3] cpuidle-powernv : forced wakeup for stop states Date: Fri, 12 Jul 2019 02:04:55 -0500 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190712070457.55242-1-huntbag@linux.vnet.ibm.com> References: <20190712070457.55242-1-huntbag@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 19071207-4275-0000-0000-0000034C64FD X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19071207-4276-0000-0000-0000385C6E0C Message-Id: <20190712070457.55242-2-huntbag@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-07-12_02:, , 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-1907120072 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ego@linux.vnet.ibm.com, daniel.lezcano@linaro.org, rjw@rjwysocki.net, npiggin@gmail.com, Abhishek Goel , dja@axtens.net Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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. v3 : Cleanly handle setting/resetting of decrementer so as to not break irq work v4 : Changed type and name of set/reset decrementer fucntion Handled irq_work_pending in try_set_dec_before_idle arch/powerpc/include/asm/time.h | 2 ++ arch/powerpc/kernel/time.c | 43 +++++++++++++++++++++++++++++++ drivers/cpuidle/cpuidle-powernv.c | 40 ++++++++++++++++++++++++++++ 3 files changed, 85 insertions(+) diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/time.h index 54f4ec1f9fab..294a472ce161 100644 --- a/arch/powerpc/include/asm/time.h +++ b/arch/powerpc/include/asm/time.h @@ -188,6 +188,8 @@ static inline unsigned long tb_ticks_since(unsigned long tstamp) extern u64 mulhdu(u64, u64); #endif +extern bool try_set_dec_before_idle(u64 timeout); +extern void try_reset_dec_after_idle(void); extern void div128_by_32(u64 dividend_high, u64 dividend_low, unsigned divisor, struct div_result *dr); diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 694522308cd5..d004c0d8e099 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -576,6 +576,49 @@ void arch_irq_work_raise(void) #endif /* CONFIG_IRQ_WORK */ +/* + * This function tries setting decrementer before entering into idle. + * Returns true if we have reprogrammed the decrementer for idle. + * Returns false if the decrementer is unchanged. + */ +bool try_set_dec_before_idle(u64 timeout) +{ + u64 *next_tb = this_cpu_ptr(&decrementers_next_tb); + u64 now = get_tb_or_rtc(); + + if (now + timeout > *next_tb) + return false; + + set_dec(timeout); + if (test_irq_work_pending()) + set_dec(1); + + return true; +} + +/* + * This function gets called if we have set decrementer before + * entering into idle. It tries to reset/restore the decrementer + * to its original value. + */ +void try_reset_dec_after_idle(void) +{ + u64 now; + u64 *next_tb; + + if (test_irq_work_pending()) + return; + + now = get_tb_or_rtc(); + next_tb = this_cpu_ptr(&decrementers_next_tb); + if (now >= *next_tb) + return; + + set_dec(*next_tb - now); + if (test_irq_work_pending()) + set_dec(1); +} + /* * timer_interrupt - gets called when the decrementer overflows, * with interrupts disabled. diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c index 84b1ebe212b3..17e20e408ffe 100644 --- a/drivers/cpuidle/cpuidle-powernv.c +++ b/drivers/cpuidle/cpuidle-powernv.c @@ -21,6 +21,7 @@ #include #include #include +#include /* * Expose only those Hardware idle states via the cpuidle framework @@ -46,6 +47,26 @@ 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 +165,27 @@ static int stop_loop(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { + u64 timeout_tb; + bool forced_wakeup = false; + + timeout_tb = forced_wakeup_timeout(dev, drv, index); + + /* Ensure that the timeout is at least one microsecond + * greater than current decrement value. Else, we will + * unnecesarily wakeup again within a microsecond if we + * set decrementer with such timeout value. + */ + timeout_tb += 512; + + if (timeout_tb) + forced_wakeup = try_set_dec_before_idle(timeout_tb); + power9_idle_type(stop_psscr_table[index].val, stop_psscr_table[index].mask); + + if (forced_wakeup) + try_reset_dec_after_idle(); + return index; }