linux-kernel - [PATCH] trace: reorder struct ring_buffer_per

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Date:	Thu, 25 Mar 2010 11:27:36 +0000
From:	Richard Kennedy <richard@....demon.co.uk>
To:	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>
Cc:	lkml <linux-kernel@...r.kernel.org>
Subject: [PATCH] trace: reorder struct ring_buffer_per_cpu to remove
 padding on 64bit

Reorder structure to remove 8 bytes of padding on 64 bit builds.
This shrinks the size to 128 bytes so allowing allocation from a smaller
slab & needed one fewer cache lines.

Signed-off-by: Richard Kennedy <richard@....demon.co.uk>
----
patch against 2.6.34-rc2
compiled & booted on x86_64

regards
Richard

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 05a9f83..421db5e 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -422,6 +422,7 @@ int ring_buffer_print_page_header(struct trace_seq
*s)
  */
 struct ring_buffer_per_cpu {
 	int				cpu;
+	atomic_t			record_disabled;
 	struct ring_buffer		*buffer;
 	spinlock_t			reader_lock;	/* serialize readers */
 	arch_spinlock_t			lock;
@@ -439,7 +440,6 @@ struct ring_buffer_per_cpu {
 	unsigned long			read;
 	u64				write_stamp;
 	u64				read_stamp;
-	atomic_t			record_disabled;
 };
 
 struct ring_buffer {


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