linux-kernel - [PATCH 2/7] workqueue: Re-order struct worker fields

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Message-Id: <20230518030033.4163274-3-tj@kernel.org>
Date:   Wed, 17 May 2023 17:00:28 -1000
From:   Tejun Heo <tj@...nel.org>
To:     jiangshanlai@...il.com
Cc:     torvalds@...ux-foundation.org, peterz@...radead.org,
        linux-kernel@...r.kernel.org, kernel-team@...a.com,
        Tejun Heo <tj@...nel.org>
Subject: [PATCH 2/7] workqueue: Re-order struct worker fields

struct worker was laid out with the intent that all fields that are modified
for each work item execution are in the first cacheline. However, this
hasn't been true for a while with the addition of ->last_func. Let's just
collect hot fields together at the top.

Move ->sleeping in the hole after ->current_color and move ->lst_func right
below. While at it, drop the cacheline comment which isn't useful anymore.

Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Lai Jiangshan <jiangshanlai@...il.com>
---
 kernel/workqueue_internal.h | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/kernel/workqueue_internal.h b/kernel/workqueue_internal.h
index e00b1204a8e9..0600f04ceeb2 100644
--- a/kernel/workqueue_internal.h
+++ b/kernel/workqueue_internal.h
@@ -32,9 +32,12 @@ struct worker {
 	work_func_t		current_func;	/* L: current_work's fn */
 	struct pool_workqueue	*current_pwq;	/* L: current_work's pwq */
 	unsigned int		current_color;	/* L: current_work's color */
-	struct list_head	scheduled;	/* L: scheduled works */
+	int			sleeping;	/* None */
+
+	/* used by the scheduler to determine a worker's last known identity */
+	work_func_t		last_func;	/* L: last work's fn */
 
-	/* 64 bytes boundary on 64bit, 32 on 32bit */
+	struct list_head	scheduled;	/* L: scheduled works */
 
 	struct task_struct	*task;		/* I: worker task */
 	struct worker_pool	*pool;		/* A: the associated pool */
@@ -45,7 +48,6 @@ struct worker {
 	unsigned long		last_active;	/* L: last active timestamp */
 	unsigned int		flags;		/* X: flags */
 	int			id;		/* I: worker id */
-	int			sleeping;	/* None */
 
 	/*
 	 * Opaque string set with work_set_desc().  Printed out with task
@@ -55,9 +57,6 @@ struct worker {
 
 	/* used only by rescuers to point to the target workqueue */
 	struct workqueue_struct	*rescue_wq;	/* I: the workqueue to rescue */
-
-	/* used by the scheduler to determine a worker's last known identity */
-	work_func_t		last_func;
 };
 
 /**
-- 
2.40.1