[PATCH] stop_machine: struct cpu_stopper, remove alignment padding on 64 bits

[PATCH] stop_machine: struct cpu_stopper, remove alignment padding on 64 bits

[Richard Kennedy]

Reorder elements in structure cpu_stopper to remove alignment padding on
64 bit builds, this shrinks its size from 40 to 32 bytes saving 8 bytes
per cpu.

Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
---
patch against 2.6.35
compiled & tested on x86_64

regards
Richard


diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 70f8d90..4372ccb 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -35,9 +35,9 @@ struct cpu_stop_done {
 /* the actual stopper, one per every possible cpu, enabled on online cpus */
 struct cpu_stopper {
 	spinlock_t		lock;
+	bool			enabled;	/* is this stopper enabled? */
 	struct list_head	works;		/* list of pending works */
 	struct task_struct	*thread;	/* stopper thread */
-	bool			enabled;	/* is this stopper enabled? */
 };
 
 static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);

Re: [PATCH] stop_machine: struct cpu_stopper, remove alignment padding on 64 bits

[Tejun Heo]

Hello,

On 08/05/2010 01:11 PM, Richard Kennedy wrote:
> Reorder elements in structure cpu_stopper to remove alignment padding on
> 64 bit builds, this shrinks its size from 40 to 32 bytes saving 8 bytes
> per cpu.
> 
> Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>

Acked-by: Tejun Heo <tj@kernel.org>

Andrew, do you mind routing this one through your tree?

  http://lkml.org/lkml/2010/8/5/168

Thank you.

-- 
tejun

Re: [PATCH] stop_machine: struct cpu_stopper, remove alignment padding on 64 bits

[Peter Zijlstra]

On Thu, 2010-08-05 at 12:11 +0100, Richard Kennedy wrote:
> Reorder elements in structure cpu_stopper to remove alignment padding on
> 64 bit builds, this shrinks its size from 40 to 32 bytes saving 8 bytes
> per cpu.
> 
> Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>

Looks good to me. Tejun will you take it or should I send it Ingo wards?

> ---
> diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
> index 70f8d90..4372ccb 100644
> --- a/kernel/stop_machine.c
> +++ b/kernel/stop_machine.c
> @@ -35,9 +35,9 @@ struct cpu_stop_done {
>  /* the actual stopper, one per every possible cpu, enabled on online cpus */
>  struct cpu_stopper {
>  	spinlock_t		lock;
> +	bool			enabled;	/* is this stopper enabled? */
>  	struct list_head	works;		/* list of pending works */
>  	struct task_struct	*thread;	/* stopper thread */
> -	bool			enabled;	/* is this stopper enabled? */
>  };
>  
>  static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);
> 
> 

Re: [PATCH] stop_machine: struct cpu_stopper, remove alignment padding on 64 bits

[Tejun Heo]

Hello, Peter.

On 08/05/2010 01:40 PM, Peter Zijlstra wrote:
> On Thu, 2010-08-05 at 12:11 +0100, Richard Kennedy wrote:
>> Reorder elements in structure cpu_stopper to remove alignment padding on
>> 64 bit builds, this shrinks its size from 40 to 32 bytes saving 8 bytes
>> per cpu.
>>
>> Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
> 
> Looks good to me. Tejun will you take it or should I send it Ingo wards?

I already asked whether Andrew could take it but routing through
Ingo's tree would be good too.  Let's wait for Andrew a bit for now.

Thank you.

-- 
tejun