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=-13.0 required=3.0 tests=BAYES_00, 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 8444EC433DF for ; Wed, 29 Jul 2020 06:48:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E11620809 for ; Wed, 29 Jul 2020 06:48:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727069AbgG2Gr5 (ORCPT ); Wed, 29 Jul 2020 02:47:57 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:5756 "EHLO mx0b-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726367AbgG2Gry (ORCPT ); Wed, 29 Jul 2020 02:47:54 -0400 Received: from pps.filterd (m0127361.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 06T6WjnN140771; Wed, 29 Jul 2020 02:47:49 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 32jpwdc5uw-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 29 Jul 2020 02:47:49 -0400 Received: from m0127361.ppops.net (m0127361.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 06T6Y0Dv144223; Wed, 29 Jul 2020 02:47:48 -0400 Received: from ppma02dal.us.ibm.com (a.bd.3ea9.ip4.static.sl-reverse.com [169.62.189.10]) by mx0a-001b2d01.pphosted.com with ESMTP id 32jpwdc5tu-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 29 Jul 2020 02:47:47 -0400 Received: from pps.filterd (ppma02dal.us.ibm.com [127.0.0.1]) by ppma02dal.us.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 06T6Ugl3004588; Wed, 29 Jul 2020 06:47:46 GMT Received: from b01cxnp23032.gho.pok.ibm.com (b01cxnp23032.gho.pok.ibm.com [9.57.198.27]) by ppma02dal.us.ibm.com with ESMTP id 32gcy4fhd9-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 29 Jul 2020 06:47:46 +0000 Received: from b01ledav005.gho.pok.ibm.com (b01ledav005.gho.pok.ibm.com [9.57.199.110]) by b01cxnp23032.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 06T6ljLM44564816 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 29 Jul 2020 06:47:46 GMT Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DFAC7AE05F; Wed, 29 Jul 2020 06:47:45 +0000 (GMT) Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 40635AE060; Wed, 29 Jul 2020 06:47:45 +0000 (GMT) Received: from sofia.ibm.com (unknown [9.85.85.173]) by b01ledav005.gho.pok.ibm.com (Postfix) with ESMTP; Wed, 29 Jul 2020 06:47:45 +0000 (GMT) Received: by sofia.ibm.com (Postfix, from userid 1000) id B7D562E2FF5; Wed, 29 Jul 2020 12:17:39 +0530 (IST) From: "Gautham R. Shenoy" To: Nicholas Piggin , Anton Blanchard , Nathan Lynch , Michael Ellerman , Michael Neuling , Vaidyanathan Srinivasan Cc: linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, "Gautham R. Shenoy" Subject: [PATCH v2 3/3] cpuidle-pseries : Fixup exit latency for CEDE(0) Date: Wed, 29 Jul 2020 12:17:34 +0530 Message-Id: <1596005254-25753-4-git-send-email-ego@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1596005254-25753-1-git-send-email-ego@linux.vnet.ibm.com> References: <1596005254-25753-1-git-send-email-ego@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-07-29_03:2020-07-28,2020-07-29 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 mlxlogscore=999 mlxscore=0 bulkscore=0 impostorscore=0 spamscore=0 adultscore=0 suspectscore=0 clxscore=1015 phishscore=0 lowpriorityscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007290043 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org From: "Gautham R. Shenoy" We are currently assuming that CEDE(0) has exit latency 10us, since there is no way for us to query from the platform. However, if the wakeup latency of an Extended CEDE state is smaller than 10us, then we can be sure that the exit latency of CEDE(0) cannot be more than that. that. In this patch, we fix the exit latency of CEDE(0) if we discover an Extended CEDE state with wakeup latency smaller than 10us. Benchmark results: ebizzy: 2 ebizzy threads bound to the same big-core. 25% improvement in the avg records/s with patch. x without_patch + with_patch N Min Max Median Avg Stddev x 10 2491089 5834307 5398375 4244335 1596244.9 + 10 2893813 5834474 5832448 5327281.3 1055941.4 context_switch2 : There is no major regression observed with this patch as seen from the context_switch2 benchmark. context_switch2 across CPU0 CPU1 (Both belong to same big-core, but different small cores). We observe a minor 0.14% regression in the number of context-switches (higher is better). x without_patch + with_patch N Min Max Median Avg Stddev x 500 348872 362236 354712 354745.69 2711.827 + 500 349422 361452 353942 354215.4 2576.9258 Difference at 99.0% confidence -530.288 +/- 430.963 -0.149484% +/- 0.121485% (Student's t, pooled s = 2645.24) context_switch2 across CPU0 CPU8 (Different big-cores). We observe a 0.37% improvement in the number of context-switches (higher is better). x without_patch + with_patch N Min Max Median Avg Stddev x 500 287956 294940 288896 288977.23 646.59295 + 500 288300 294646 289582 290064.76 1161.9992 Difference at 99.0% confidence 1087.53 +/- 153.194 0.376337% +/- 0.0530125% (Student's t, pooled s = 940.299) schbench: No major difference could be seen until the 99.9th percentile. Without-patch Latency percentiles (usec) 50.0th: 29 75.0th: 39 90.0th: 49 95.0th: 59 *99.0th: 13104 99.5th: 14672 99.9th: 15824 min=0, max=17993 With-patch: Latency percentiles (usec) 50.0th: 29 75.0th: 40 90.0th: 50 95.0th: 61 *99.0th: 13648 99.5th: 14768 99.9th: 15664 min=0, max=29812 Reviewed-by: Vaidyanathan Srinivasan Signed-off-by: Gautham R. Shenoy --- drivers/cpuidle/cpuidle-pseries.c | 34 ++++++++++++++++++++++++++++++++-- 1 file changed, 32 insertions(+), 2 deletions(-) diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c index b1dc24d..0b2f115 100644 --- a/drivers/cpuidle/cpuidle-pseries.c +++ b/drivers/cpuidle/cpuidle-pseries.c @@ -334,12 +334,42 @@ static int pseries_cpuidle_driver_init(void) static int add_pseries_idle_states(void) { int nr_states = 2; /* By default we have snooze, CEDE */ + int i; + u64 min_latency_us = dedicated_states[1].exit_latency; /* CEDE latency */ if (parse_cede_parameters()) return nr_states; - pr_info("cpuidle : Skipping the %d Extended CEDE idle states\n", - nr_xcede_records); + for (i = 0; i < nr_xcede_records; i++) { + u64 latency_tb = xcede_records[i].wakeup_latency_tb_ticks; + u64 latency_us = tb_to_ns(latency_tb) / NSEC_PER_USEC; + + if (latency_us < min_latency_us) + min_latency_us = latency_us; + } + + /* + * We are currently assuming that CEDE(0) has exit latency + * 10us, since there is no way for us to query from the + * platform. + * + * However, if the wakeup latency of an Extended CEDE state is + * smaller than 10us, then we can be sure that CEDE(0) + * requires no more than that. + * + * Perform the fix-up. + */ + if (min_latency_us < dedicated_states[1].exit_latency) { + u64 cede0_latency = min_latency_us - 1; + + if (cede0_latency <= 0) + cede0_latency = min_latency_us; + + dedicated_states[1].exit_latency = cede0_latency; + dedicated_states[1].target_residency = 10 * (cede0_latency); + pr_info("cpuidle : Fixed up CEDE exit latency to %llu us\n", + cede0_latency); + } return nr_states; } -- 1.9.4