From patchwork Thu Jul 30 05:32:55 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Gautham R Shenoy X-Patchwork-Id: 1338652 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 4BHJz309Nlz9sRK for ; Thu, 30 Jul 2020 15:35:26 +1000 (AEST) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4BHJz23N7bzDqBs for ; Thu, 30 Jul 2020 15:35:26 +1000 (AEST) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Received: from ozlabs.org (bilbo.ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4BHJwd6GklzDqnl for ; Thu, 30 Jul 2020 15:33:21 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com Received: from ozlabs.org (bilbo.ozlabs.org [IPv6:2401:3900:2:1::2]) by bilbo.ozlabs.org (Postfix) with ESMTP id 4BHJwc5rTTz9CLb for ; Thu, 30 Jul 2020 15:33:20 +1000 (AEST) Received: by ozlabs.org (Postfix) id 4BHJwc47Bkz9sSt; Thu, 30 Jul 2020 15:33:20 +1000 (AEST) Delivered-To: linuxppc-dev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=linux.vnet.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=ego@linux.vnet.ibm.com; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (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 ozlabs.org (Postfix) with ESMTPS id 4BHJwc0rLyz9sRX; Thu, 30 Jul 2020 15:33:19 +1000 (AEST) Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 06U5X3Gg179093; Thu, 30 Jul 2020 01:33:18 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 32jy8whq86-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 30 Jul 2020 01:33:18 -0400 Received: from m0098396.ppops.net (m0098396.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 06U5XIST179933; Thu, 30 Jul 2020 01:33:18 -0400 Received: from ppma04dal.us.ibm.com (7a.29.35a9.ip4.static.sl-reverse.com [169.53.41.122]) by mx0a-001b2d01.pphosted.com with ESMTP id 32jy8whq7n-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 30 Jul 2020 01:33:18 -0400 Received: from pps.filterd (ppma04dal.us.ibm.com [127.0.0.1]) by ppma04dal.us.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 06U5OQIM030866; Thu, 30 Jul 2020 05:33:17 GMT Received: from b01cxnp22034.gho.pok.ibm.com (b01cxnp22034.gho.pok.ibm.com [9.57.198.24]) by ppma04dal.us.ibm.com with ESMTP id 32gcq1ss2x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 30 Jul 2020 05:33:17 +0000 Received: from b01ledav005.gho.pok.ibm.com (b01ledav005.gho.pok.ibm.com [9.57.199.110]) by b01cxnp22034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 06U5XGQg48300468 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 30 Jul 2020 05:33:16 GMT Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5FCBDAE067; Thu, 30 Jul 2020 05:33:16 +0000 (GMT) Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BE412AE05F; Thu, 30 Jul 2020 05:33:15 +0000 (GMT) Received: from sofia.ibm.com (unknown [9.102.0.230]) by b01ledav005.gho.pok.ibm.com (Postfix) with ESMTP; Thu, 30 Jul 2020 05:33:15 +0000 (GMT) Received: by sofia.ibm.com (Postfix, from userid 1000) id D80F82E2EB8; Thu, 30 Jul 2020 11:03:09 +0530 (IST) From: "Gautham R. Shenoy" To: Nicholas Piggin , Anton Blanchard , Nathan Lynch , Michael Ellerman , Michael Neuling , Vaidyanathan Srinivasan Subject: [PATCH v3 1/3] cpuidle-pseries: Set the latency-hint before entering CEDE Date: Thu, 30 Jul 2020 11:02:55 +0530 Message-Id: <1596087177-30329-2-git-send-email-ego@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1596087177-30329-1-git-send-email-ego@linux.vnet.ibm.com> References: <1596087177-30329-1-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=2020-07-30_03:2020-07-29, 2020-07-30 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 phishscore=0 mlxscore=0 bulkscore=0 malwarescore=0 adultscore=0 clxscore=1015 lowpriorityscore=0 suspectscore=0 mlxlogscore=850 spamscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007300042 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: linuxppc-dev@ozlabs.org, "Gautham R. Shenoy" , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: "Gautham R. Shenoy" As per the PAPR, each H_CEDE call is associated with a latency-hint to be passed in the VPA field "cede_latency_hint". The CEDE states that we were implicitly entering so far is CEDE with latency-hint = 0. This patch explicitly sets the latency hint corresponding to the CEDE state that we are currently entering. While at it, we save the previous hint, to be restored once we wakeup from CEDE. This will be required in the future when we expose extended-cede states through the cpuidle framework, where each of them will have a different cede-latency hint. Signed-off-by: Gautham R. Shenoy --- v2-->v3 : Got rid of the usused NR_CEDE_STATES definition drivers/cpuidle/cpuidle-pseries.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c index 3e058ad2..f5865a2 100644 --- a/drivers/cpuidle/cpuidle-pseries.c +++ b/drivers/cpuidle/cpuidle-pseries.c @@ -86,19 +86,26 @@ static void check_and_cede_processor(void) } } +#define NR_DEDICATED_STATES 2 /* snooze, CEDE */ + +u8 cede_latency_hint[NR_DEDICATED_STATES]; static int dedicated_cede_loop(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { + u8 old_latency_hint; pseries_idle_prolog(); get_lppaca()->donate_dedicated_cpu = 1; + old_latency_hint = get_lppaca()->cede_latency_hint; + get_lppaca()->cede_latency_hint = cede_latency_hint[index]; HMT_medium(); check_and_cede_processor(); local_irq_disable(); get_lppaca()->donate_dedicated_cpu = 0; + get_lppaca()->cede_latency_hint = old_latency_hint; pseries_idle_epilog(); @@ -130,7 +137,7 @@ static int shared_cede_loop(struct cpuidle_device *dev, /* * States for dedicated partition case. */ -static struct cpuidle_state dedicated_states[] = { +static struct cpuidle_state dedicated_states[NR_DEDICATED_STATES] = { { /* Snooze */ .name = "snooze", .desc = "snooze", @@ -233,7 +240,7 @@ static int pseries_idle_probe(void) max_idle_state = ARRAY_SIZE(shared_states); } else { cpuidle_state_table = dedicated_states; - max_idle_state = ARRAY_SIZE(dedicated_states); + max_idle_state = NR_DEDICATED_STATES; } } else return -ENODEV; From patchwork Thu Jul 30 05:32:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Gautham R Shenoy X-Patchwork-Id: 1338654 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 4BHK4X6d41z9sRW for ; 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Thu, 30 Jul 2020 05:33:16 GMT Received: from b03ledav003.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5741F6A057; Thu, 30 Jul 2020 05:33:16 +0000 (GMT) Received: from b03ledav003.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6F8E16A04D; Thu, 30 Jul 2020 05:33:15 +0000 (GMT) Received: from sofia.ibm.com (unknown [9.102.0.230]) by b03ledav003.gho.boulder.ibm.com (Postfix) with ESMTP; Thu, 30 Jul 2020 05:33:15 +0000 (GMT) Received: by sofia.ibm.com (Postfix, from userid 1000) id E6F5D2E2F45; Thu, 30 Jul 2020 11:03:09 +0530 (IST) From: "Gautham R. Shenoy" To: Nicholas Piggin , Anton Blanchard , Nathan Lynch , Michael Ellerman , Michael Neuling , Vaidyanathan Srinivasan Subject: [PATCH v3 2/3] cpuidle-pseries: Add function to parse extended CEDE records Date: Thu, 30 Jul 2020 11:02:56 +0530 Message-Id: <1596087177-30329-3-git-send-email-ego@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1596087177-30329-1-git-send-email-ego@linux.vnet.ibm.com> References: <1596087177-30329-1-git-send-email-ego@linux.vnet.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-07-30_03:2020-07-29, 2020-07-30 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 lowpriorityscore=0 malwarescore=0 phishscore=0 mlxlogscore=999 clxscore=1015 priorityscore=1501 adultscore=0 bulkscore=0 spamscore=0 impostorscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007300038 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: linuxppc-dev@ozlabs.org, "Gautham R. Shenoy" , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: "Gautham R. Shenoy" Currently we use CEDE with latency-hint 0 as the only other idle state on a dedicated LPAR apart from the polling "snooze" state. The platform might support additional extended CEDE idle states, which can be discovered through the "ibm,get-system-parameter" rtas-call made with CEDE_LATENCY_TOKEN. This patch adds a function to obtain information about the extended CEDE idle states from the platform and parse the contents to populate an array of extended CEDE states. These idle states thus discovered will be added to the cpuidle framework in the next patch. dmesg on a POWER8 and POWER9 LPAR, demonstrating the output of parsing the extended CEDE latency parameters are as follows POWER8 [ 10.093279] xcede : xcede_record_size = 10 [ 10.093285] xcede : Record 0 : hint = 1, latency = 0x3c00 tb ticks, Wake-on-irq = 1 [ 10.093291] xcede : Record 1 : hint = 2, latency = 0x4e2000 tb ticks, Wake-on-irq = 0 [ 10.093297] cpuidle : Skipping the 2 Extended CEDE idle states POWER9 [ 5.913180] xcede : xcede_record_size = 10 [ 5.913183] xcede : Record 0 : hint = 1, latency = 0x400 tb ticks, Wake-on-irq = 1 [ 5.913188] xcede : Record 1 : hint = 2, latency = 0x3e8000 tb ticks, Wake-on-irq = 0 [ 5.913193] cpuidle : Skipping the 2 Extended CEDE idle states Signed-off-by: Gautham R. Shenoy --- v2-->v3 : Cleaned up parse_cede_parameters(). Silenced some sparse warnings. drivers/cpuidle/cpuidle-pseries.c | 142 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 142 insertions(+) diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c index f5865a2..f528da7 100644 --- a/drivers/cpuidle/cpuidle-pseries.c +++ b/drivers/cpuidle/cpuidle-pseries.c @@ -21,6 +21,7 @@ #include #include #include +#include static struct cpuidle_driver pseries_idle_driver = { .name = "pseries_idle", @@ -87,6 +88,137 @@ static void check_and_cede_processor(void) } #define NR_DEDICATED_STATES 2 /* snooze, CEDE */ +/* + * XCEDE : Extended CEDE states discovered through the + * "ibm,get-systems-parameter" rtas-call with the token + * CEDE_LATENCY_TOKEN + */ +#define MAX_XCEDE_STATES 4 +#define XCEDE_LATENCY_RECORD_SIZE 10 +#define XCEDE_LATENCY_PARAM_MAX_LENGTH (2 + 2 + \ + (MAX_XCEDE_STATES * XCEDE_LATENCY_RECORD_SIZE)) + +/* + * Section 7.3.16 System Parameters Option of PAPR version 2.8.1 has a + * table with all the parameters to ibm,get-system-parameters. + * CEDE_LATENCY_TOKEN corresponds to the token value for Cede Latency + * Settings Information. + */ +#define CEDE_LATENCY_TOKEN 45 + +/* + * If the platform supports the cede latency settings + * information system parameter it must provide the following + * information in the NULL terminated parameter string: + * + * a. The first byte is the length “N” of each cede + * latency setting record minus one (zero indicates a length + * of 1 byte). + * + * b. For each supported cede latency setting a cede latency + * setting record consisting of the first “N” bytes as per + * the following table. + * + * ----------------------------- + * | Field | Field | + * | Name | Length | + * ----------------------------- + * | Cede Latency | 1 Byte | + * | Specifier Value | | + * ----------------------------- + * | Maximum wakeup | | + * | latency in | 8 Bytes| + * | tb-ticks | | + * ----------------------------- + * | Responsive to | | + * | external | 1 Byte | + * | interrupts | | + * ----------------------------- + * + * This version has cede latency record size = 10. + * + * The structure xcede_latency_payload represents a) and b) with + * xcede_latency_record representing the table in b). + * + * xcede_latency_parameter is what gets returned by + * ibm,get-systems-parameter rtas-call when made with + * CEDE_LATENCY_TOKEN. + * + * These structures are only used to represent the data sent obtained + * by the rtas-call. The data is in Big-Endian. + */ +struct xcede_latency_record { + u8 hint; + __be64 latency_ticks; + u8 wake_on_irqs; +} __packed; + +struct xcede_latency_payload { + u8 record_size; + struct xcede_latency_record records[MAX_XCEDE_STATES]; +} __packed; + +struct xcede_latency_parameter { + __be16 payload_size; + struct xcede_latency_payload payload; + u8 null_char; +} __packed; + +static unsigned int nr_xcede_records; +static struct xcede_latency_parameter xcede_latency_parameter __initdata; + +static int __init parse_cede_parameters(void) +{ + int ret, i; + u16 payload_size; + u8 xcede_record_size; + u32 total_xcede_records_size; + struct xcede_latency_payload *payload; + + memset(&xcede_latency_parameter, 0, sizeof(xcede_latency_parameter)); + + ret = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1, + NULL, CEDE_LATENCY_TOKEN, __pa(&xcede_latency_parameter), + sizeof(xcede_latency_parameter)); + + if (ret) { + pr_err("xcede: Error parsing CEDE_LATENCY_TOKEN\n"); + return ret; + } + + payload_size = be16_to_cpu(xcede_latency_parameter.payload_size); + payload = &xcede_latency_parameter.payload; + + xcede_record_size = payload->record_size + 1; + + if (xcede_record_size != XCEDE_LATENCY_RECORD_SIZE) { + pr_err("xcede : Expected record-size %d. Observed size %d.\n", + XCEDE_LATENCY_RECORD_SIZE, xcede_record_size); + return -EINVAL; + } + + pr_info("xcede : xcede_record_size = %d\n", xcede_record_size); + + /* + * Since the payload_length includes the last NULL byte and + * the xcede_record_size, the remaining bytes correspond to + * array of all cede_latency settings. + */ + total_xcede_records_size = payload_size - 2; + nr_xcede_records = total_xcede_records_size / xcede_record_size; + + for (i = 0; i < nr_xcede_records; i++) { + struct xcede_latency_record *record = &payload->records[i]; + u8 hint = record->hint; + u8 wake_on_irqs = record->wake_on_irqs; + u64 latency_ticks = be64_to_cpu(record->latency_ticks); + + pr_info("xcede : Record %d : hint = %u, latency = 0x%llx tb ticks, Wake-on-irq = %u\n", + i, hint, latency_ticks, wake_on_irqs); + } + + return 0; +} u8 cede_latency_hint[NR_DEDICATED_STATES]; static int dedicated_cede_loop(struct cpuidle_device *dev, @@ -218,6 +350,15 @@ static int pseries_cpuidle_driver_init(void) return 0; } +static void __init parse_xcede_idle_states(void) +{ + if (parse_cede_parameters()) + return; + + pr_info("cpuidle : Skipping the %d Extended CEDE idle states\n", + nr_xcede_records); +} + /* * pseries_idle_probe() * Choose state table for shared versus dedicated partition @@ -239,6 +380,7 @@ static int pseries_idle_probe(void) cpuidle_state_table = shared_states; max_idle_state = ARRAY_SIZE(shared_states); } else { + parse_xcede_idle_states(); cpuidle_state_table = dedicated_states; max_idle_state = NR_DEDICATED_STATES; } From patchwork Thu Jul 30 05:32:57 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Gautham R Shenoy X-Patchwork-Id: 1338666 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 4BHKBH4Zv3z9sRW for ; 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Shenoy" To: Nicholas Piggin , Anton Blanchard , Nathan Lynch , Michael Ellerman , Michael Neuling , Vaidyanathan Srinivasan Subject: [PATCH v3 3/3] cpuidle-pseries : Fixup exit latency for CEDE(0) Date: Thu, 30 Jul 2020 11:02:57 +0530 Message-Id: <1596087177-30329-4-git-send-email-ego@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1596087177-30329-1-git-send-email-ego@linux.vnet.ibm.com> References: <1596087177-30329-1-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=2020-07-30_03:2020-07-29, 2020-07-30 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 mlxscore=0 mlxlogscore=999 phishscore=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 spamscore=0 adultscore=0 bulkscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007300038 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: linuxppc-dev@ozlabs.org, "Gautham R. Shenoy" , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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: On POWER8, this patch does not have any impact since the advertized latency of Extended CEDE (1) is 30us which is higher than the default latency of CEDE (0) which is 10us. On POWER9 we see improvement the single-threaded performance of ebizzy, and no regression in the wakeup latency or the number of context-switches. 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 Signed-off-by: Gautham R. Shenoy --- v2-->v3 : Made notation consistent with first two patches. drivers/cpuidle/cpuidle-pseries.c | 41 +++++++++++++++++++++++++++++++++++++-- 1 file changed, 39 insertions(+), 2 deletions(-) diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c index f528da7..8d19820 100644 --- a/drivers/cpuidle/cpuidle-pseries.c +++ b/drivers/cpuidle/cpuidle-pseries.c @@ -350,13 +350,50 @@ static int pseries_cpuidle_driver_init(void) return 0; } -static void __init parse_xcede_idle_states(void) +static void __init fixup_cede0_latency(void) { + int i; + u64 min_latency_us = dedicated_states[1].exit_latency; /* CEDE latency */ + struct xcede_latency_payload *payload; + if (parse_cede_parameters()) return; pr_info("cpuidle : Skipping the %d Extended CEDE idle states\n", nr_xcede_records); + + payload = &xcede_latency_parameter.payload; + for (i = 0; i < nr_xcede_records; i++) { + struct xcede_latency_record *record = &payload->records[i]; + u64 latency_tb = be64_to_cpu(record->latency_ticks); + u64 latency_us = tb_to_ns(latency_tb) / NSEC_PER_USEC; + + if (latency_us < min_latency_us) + min_latency_us = latency_us; + } + + /* + * By default, we assume 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); + } + } /* @@ -380,7 +417,7 @@ static int pseries_idle_probe(void) cpuidle_state_table = shared_states; max_idle_state = ARRAY_SIZE(shared_states); } else { - parse_xcede_idle_states(); + fixup_cede0_latency(); cpuidle_state_table = dedicated_states; max_idle_state = NR_DEDICATED_STATES; }