linux-kernel - [tip: core/rseq] sched/mmcid: Cacheline align MM CID storage

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Message-ID: <176363760634.498.1894935121666974461.tip-bot2@tip-bot2>
Date: Thu, 20 Nov 2025 11:20:06 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: core/rseq] sched/mmcid: Cacheline align MM CID storage

The following commit has been merged into the core/rseq branch of tip:

Commit-ID:     be4463fa2c7185823d2989562162d578b45a89ae
Gitweb:        https://git.kernel.org/tip/be4463fa2c7185823d2989562162d578b45a89ae
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Wed, 19 Nov 2025 18:26:49 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 20 Nov 2025 12:14:53 +01:00

sched/mmcid: Cacheline align MM CID storage

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@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Link: https://patch.msgid.link/20251119172549.194111661@linutronix.de
---
 include/linux/rseq_types.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/rseq_types.h b/include/linux/rseq_types.h
index e444dd2..d7e8071 100644
--- 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 { };