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Shenoy" , K Prateek Nayak , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Xin Li , "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" , Tim Chen , "David Vernet" , Julia Lawall , , Subject: [PATCH v2 04/14] x86/thread_info: Introduce TIF_NOTIFY_IPI flag Date: Thu, 13 Jun 2024 18:16:03 +0000 Message-ID: <20240613181613.4329-5-kprateek.nayak@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240613181613.4329-1-kprateek.nayak@amd.com> References: <20240613181613.4329-1-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: BL6PEPF00022570:EE_|PH7PR12MB6933:EE_ X-MS-Office365-Filtering-Correlation-Id: 34e246c6-4498-4d4e-3bf1-08dc8bd550d7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; ARA:13230035|376009|7416009|1800799019|36860700008|82310400021; 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:(13230035)(376009)(7416009)(1800799019)(36860700008)(82310400021); DIR:OUT; SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Jun 2024 18:19:07.7689 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 34e246c6-4498-4d4e-3bf1-08dc8bd550d7 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: BL6PEPF00022570.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB6933 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 [baseline] tip:sched/core + TIF_NOTIFY_IPI 0.46 [54.88] tip:sched/core was at commit c793a62823d1 ("sched/core: Drop spinlocks on contention iff kernel is preemptible") 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: Xin Li 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: Tim Chen Cc: David Vernet Cc: Julia Lawall 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 --- v1..v2: o Updated benchmark numbers. --- 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 12da7dfd5ef1..640ee41b8c82 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -89,6 +89,7 @@ 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 */ @@ -112,6 +113,7 @@ 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)