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From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Gabriele Monaco <gmonaco@redhat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Michael Jeanson <mjeanson@efficios.com>,
	Jens Axboe <axboe@kernel.dk>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	"Gautham R. Shenoy" <gautham.shenoy@amd.com>,
	Florian Weimer <fweimer@redhat.com>,
	Tim Chen <tim.c.chen@intel.com>,
	Yury Norov <yury.norov@gmail.com>,
	Shrikanth Hegde <sshegde@linux.ibm.com>
Subject: [patch V4 03/20] sched/mmcid: Cacheline align MM CID storage
Date: Sun, 16 Nov 2025 21:48:39 +0100 (CET)	[thread overview]
Message-ID: <20251104075426.796873498@linutronix.de> (raw)
In-Reply-To: 20251104075053.700034556@linutronix.de

Both the per CPU storage and the data in mm_struct are heavily used in
context switch. As they can end up next to other frequently modified data,
they are subject to false sharing.

Make them cache line aligned.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/rseq_types.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/include/linux/rseq_types.h
+++ b/include/linux/rseq_types.h
@@ -112,7 +112,7 @@ struct sched_mm_cid {
  */
 struct mm_cid_pcpu {
 	unsigned int	cid;
-};
+}____cacheline_aligned_in_smp;
 
 /**
  * struct mm_mm_cid - Storage for per MM CID data
@@ -126,7 +126,7 @@ struct mm_mm_cid {
 	struct mm_cid_pcpu	__percpu *pcpu;
 	unsigned int		nr_cpus_allowed;
 	raw_spinlock_t		lock;
-};
+}____cacheline_aligned_in_smp;
 #else /* CONFIG_SCHED_MM_CID */
 struct mm_mm_cid { };
 struct sched_mm_cid { };


  parent reply	other threads:[~2025-11-16 20:48 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-11-16 20:48 [patch V4 00/20] sched: Rewrite MM CID management Thomas Gleixner
2025-11-16 20:48 ` [patch V4 01/20] sched/mmcid: Revert the complex " Thomas Gleixner
2025-11-17 16:42   ` Mathieu Desnoyers
2025-11-16 20:48 ` [patch V4 02/20] sched/mmcid: Use proper data structures Thomas Gleixner
2025-11-16 20:48 ` Thomas Gleixner [this message]
2025-11-17 16:44   ` [patch V4 03/20] sched/mmcid: Cacheline align MM CID storage Mathieu Desnoyers
2025-11-16 20:48 ` [patch V4 04/20] sched: Fixup whitespace damage Thomas Gleixner
2025-11-17 16:45   ` Mathieu Desnoyers
2025-11-16 20:48 ` [patch V4 05/20] sched/mmcid: Move scheduler code out of global header Thomas Gleixner
2025-11-19 16:17   ` Yury Norov
2025-11-16 20:48 ` [patch V4 06/20] sched/mmcid: Prevent pointless work in mm_update_cpus_allowed() Thomas Gleixner
2025-11-16 20:48 ` [patch V4 07/20] cpumask: Introduce cpumask_weighted_or() Thomas Gleixner
2025-11-16 20:48 ` [patch V4 08/20] sched/mmcid: Use cpumask_weighted_or() Thomas Gleixner
2025-11-19 16:20   ` Yury Norov
2025-11-16 20:48 ` [patch V4 09/20] cpumask: Cache num_possible_cpus() Thomas Gleixner
2025-11-17 16:48   ` Mathieu Desnoyers
2025-11-18  4:36   ` Shrikanth Hegde
2025-11-16 20:48 ` [patch V4 10/20] sched/mmcid: Convert mm CID mask to a bitmap Thomas Gleixner
2025-11-17 16:51   ` Mathieu Desnoyers
2025-11-16 20:48 ` [patch V4 11/20] signal: Move MMCID exit out of sighand lock Thomas Gleixner
2025-11-17 16:53   ` Mathieu Desnoyers
2025-11-16 20:48 ` [patch V4 12/20] sched/mmcid: Move initialization out of line Thomas Gleixner
2025-11-16 20:48 ` [patch V4 13/20] sched/mmcid: Provide precomputed maximal value Thomas Gleixner
2025-11-17 16:59   ` Mathieu Desnoyers
2025-11-16 20:49 ` [patch V4 14/20] sched/mmcid: Serialize sched_mm_cid_fork()/exit() with a mutex Thomas Gleixner
2025-11-16 20:49 ` [patch V4 15/20] sched/mmcid: Introduce per task/CPU ownership infrastructure Thomas Gleixner
2025-11-17 19:05   ` Mathieu Desnoyers
2025-11-16 20:49 ` [patch V4 16/20] sched/mmcid: Provide new scheduler CID mechanism Thomas Gleixner
2025-11-17 19:40   ` Mathieu Desnoyers
2025-11-16 20:49 ` [patch V4 17/20] sched/mmcid: Provide CID ownership mode fixup functions Thomas Gleixner
2025-11-17 19:41   ` Mathieu Desnoyers
2025-11-16 20:49 ` [patch V4 18/20] irqwork: Move data struct to a types header Thomas Gleixner
2025-11-16 20:49 ` [patch V4 19/20] sched/mmcid: Implement deferred mode change Thomas Gleixner
2025-11-16 20:49 ` [patch V4 20/20] sched/mmcid: Switch over to the new mechanism Thomas Gleixner
2025-11-17 19:45   ` Mathieu Desnoyers

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