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Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by SA2PEPF000015C6.mail.protection.outlook.com (10.167.241.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.7292.25 via Frontend Transport; Tue, 20 Feb 2024 17:17:48 +0000 Received: from BLR5CG134614W.amd.com (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Tue, 20 Feb 2024 11:17:41 -0600 From: K Prateek Nayak To: CC: "Gautham R. Shenoy" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , "Rafael J. Wysocki" , Daniel Lezcano , Peter Zijlstra , "Juri Lelli" , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , "Valentin Schneider" , Andrew Morton , Arnd Bergmann , Tim Chen , "David Vernet" , , , "K Prateek Nayak" Subject: [RFC PATCH 04/14] x86/thread_info: Introduce TIF_NOTIFY_IPI flag Date: Tue, 20 Feb 2024 22:44:47 +0530 Message-ID: <20240220171457.703-5-kprateek.nayak@amd.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240220171457.703-1-kprateek.nayak@amd.com> References: <20240220171457.703-1-kprateek.nayak@amd.com> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SA2PEPF000015C6:EE_|SA1PR12MB7441:EE_ X-MS-Office365-Filtering-Correlation-Id: 70144d14-30f0-42dd-e3fa-08dc3237dcd6 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230031)(36860700004)(46966006)(40470700004);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Feb 2024 17:17:48.8334 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 70144d14-30f0-42dd-e3fa-08dc3237dcd6 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SA2PEPF000015C6.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB7441 From: "Gautham R. Shenoy" Add support for TIF_NOTIFY_IPI on x86. With TIF_NOTIFY_IPI, a sender sending an IPI to an idle CPU in TIF_POLLING mode will set the TIF_NOTIFY_IPI flag in the target's idle tasks's thread_info to pull the CPU out of idle, as opposed to setting TIF_NEED_RESCHED previously. This avoids spurious calls to schedule_idle() in cases where an IPI does not necessarily wake up a task on the idle CPU. IPI throughput measured using a modified version of Anton Blanchard's ipistorm benchmark [1], configured to measure time taken to perform a fixed number of smp_call_function_single() (with wait set to 1), improves significantly with TIF_NOTIFY_IPI on a dual socket Ampere Server (2 x 64C) with the benchmark time reducing to less than half for 100000 IPIs between two CPUs. (Note: Only WFI idle mode was left enabled during testing to reduce variance) cmdline: insmod ipistorm.ko numipi=100000 single=1 offset=8 cpulist=8 wait=1 ================================================================== Test : ipistorm (modified) Units : Normalized runtime Interpretation: Lower is better Statistic : AMean ================================================================== kernel: time [pct imp] tip:sched/core 1.00 [0.00] tip:sched/core + TIF_NOTIFY_IPI 0.41 [59.29] tip:sched/core was at tag "sched-core-2024-01-08" at the time of testing. [ prateek: Split the changes into a separate patch, commit log ] Link: https://github.com/antonblanchard/ipistorm [1] Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" Cc: "Rafael J. Wysocki" Cc: Daniel Lezcano Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Steven Rostedt Cc: Ben Segall Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Valentin Schneider Cc: Andrew Morton Cc: Arnd Bergmann Cc: Tim Chen Cc: David Vernet Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-pm@vger.kernel.org Signed-off-by: Gautham R. Shenoy Co-developed-by: K Prateek Nayak Signed-off-by: K Prateek Nayak --- arch/x86/include/asm/thread_info.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index d63b02940747..90cdce971397 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -83,6 +83,7 @@ struct thread_info { #define TIF_NEED_RESCHED 3 /* rescheduling necessary */ #define TIF_SINGLESTEP 4 /* reenable singlestep on user return*/ #define TIF_SSBD 5 /* Speculative store bypass disable */ +#define TIF_NOTIFY_IPI 6 /* Pending IPI on TIF_POLLLING idle CPU */ #define TIF_SPEC_IB 9 /* Indirect branch speculation mitigation */ #define TIF_SPEC_L1D_FLUSH 10 /* Flush L1D on mm switches (processes) */ #define TIF_USER_RETURN_NOTIFY 11 /* notify kernel of userspace return */ @@ -106,6 +107,7 @@ struct thread_info { #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) #define _TIF_SINGLESTEP (1 << TIF_SINGLESTEP) #define _TIF_SSBD (1 << TIF_SSBD) +#define _TIF_NOTIFY_IPI (1 << TIF_NOTIFY_IPI) #define _TIF_SPEC_IB (1 << TIF_SPEC_IB) #define _TIF_SPEC_L1D_FLUSH (1 << TIF_SPEC_L1D_FLUSH) #define _TIF_USER_RETURN_NOTIFY (1 << TIF_USER_RETURN_NOTIFY)