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From: Wei Yang <richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
	lizefan.x-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org,
	hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org
Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Wei Yang
	<richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: [PATCH 2/4] cgroup: reorder cgroup_subsys fields to save 8 byte
Date: Mon,  4 Oct 2021 08:49:26 +0000	[thread overview]
Message-ID: <20211004084928.17622-2-richard.weiyang@gmail.com> (raw)
In-Reply-To: <20211004084928.17622-1-richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

On 64bit platform, struct is aligned by 8 bytes by default.

By moving cgroup_subsys.depends_on, we fit these adjacent fields into
8 bytes alignment.

Signed-off-by: Wei Yang <richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 include/linux/cgroup-defs.h | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index f6d80896daab..4649d09396fd 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -672,6 +672,15 @@ struct cgroup_subsys {
 	 */
 	bool threaded:1;
 
+	/*
+	 * A subsystem may depend on other subsystems.  When such subsystem
+	 * is enabled on a cgroup, the depended-upon subsystems are enabled
+	 * together if available.  Subsystems enabled due to dependency are
+	 * not visible to userland until explicitly enabled.  The following
+	 * specifies the mask of subsystems that this one depends on.
+	 */
+	u16 depends_on;
+
 	/* the following two fields are initialized automatically during boot */
 	int id;
 	const char *name;
@@ -698,14 +707,6 @@ struct cgroup_subsys {
 	struct cftype *dfl_cftypes;	/* for the default hierarchy */
 	struct cftype *legacy_cftypes;	/* for the legacy hierarchies */
 
-	/*
-	 * A subsystem may depend on other subsystems.  When such subsystem
-	 * is enabled on a cgroup, the depended-upon subsystems are enabled
-	 * together if available.  Subsystems enabled due to dependency are
-	 * not visible to userland until explicitly enabled.  The following
-	 * specifies the mask of subsystems that this one depends on.
-	 */
-	u16 depends_on;
 };
 
 extern struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
-- 
2.23.0


  parent reply	other threads:[~2021-10-04  8:49 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-04  8:49 [PATCH 1/4] cgroup: a u16 is enough for cgroup_subsys.depends_on Wei Yang
     [not found] ` <20211004084928.17622-1-richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2021-10-04  8:49   ` Wei Yang [this message]
2021-10-04  8:49   ` [PATCH 3/4] cgroup: simplify the cgroup descendant helper Wei Yang
2021-10-04  8:49   ` [PATCH 4/4] cgroup: use parent directly instead of cgroup_parent() Wei Yang
2021-10-04 16:30   ` [PATCH 1/4] cgroup: a u16 is enough for cgroup_subsys.depends_on Tejun Heo

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