Re: [RFC PATCH REBASED 1/3] sh: Move fpu_counter into ARCH specific thread_struct

[Vineet Gupta <Vineet.Gupta1@synopsys.com>]

Hi Paul/SH folks.

Would appreciate your ACK/NAK on this.

Thx,
-Vineet

On 09/17/2013 11:47 AM, Vineet Gupta wrote:
> Only a couple of arches (sh/x86) use fpu_counter in task_struct so it
> can be moved out into ARCH specific thread_struct, reducing the size of
> task_struct for other arches.
> 
> Compile tested sh defconfig + sh4-linux-gcc (4.6.3)
> 
> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
> Cc: Paul Mundt <lethal@linux-sh.org>
> Cc: Michel Lespinasse <walken@google.com>
> Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Jesper Nilsson <jesper.nilsson@axis.com>
> Cc: Chris Metcalf <cmetcalf@tilera.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-arch@vger.kernel.org
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: linux-sh@vger.kernel.org
> ---
>  arch/sh/include/asm/fpu.h          |  2 +-
>  arch/sh/include/asm/processor_32.h | 10 ++++++++++
>  arch/sh/include/asm/processor_64.h | 10 ++++++++++
>  arch/sh/kernel/cpu/fpu.c           |  2 +-
>  arch/sh/kernel/process_32.c        |  6 +++---
>  5 files changed, 25 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/sh/include/asm/fpu.h b/arch/sh/include/asm/fpu.h
> index 06c4281..09fc2bc 100644
> --- a/arch/sh/include/asm/fpu.h
> +++ b/arch/sh/include/asm/fpu.h
> @@ -46,7 +46,7 @@ static inline void __unlazy_fpu(struct task_struct *tsk, struct pt_regs *regs)
>  		save_fpu(tsk);
>  		release_fpu(regs);
>  	} else
> -		tsk->fpu_counter = 0;
> +		tsk->thread.fpu_counter = 0;
>  }
>  
>  static inline void unlazy_fpu(struct task_struct *tsk, struct pt_regs *regs)
> diff --git a/arch/sh/include/asm/processor_32.h b/arch/sh/include/asm/processor_32.h
> index e699a12..18e0377 100644
> --- a/arch/sh/include/asm/processor_32.h
> +++ b/arch/sh/include/asm/processor_32.h
> @@ -111,6 +111,16 @@ struct thread_struct {
>  
>  	/* Extended processor state */
>  	union thread_xstate *xstate;
> +
> +	/*
> +	 * fpu_counter contains the number of consecutive context switches
> +	 * that the FPU is used. If this is over a threshold, the lazy fpu
> +	 * saving becomes unlazy to save the trap. This is an unsigned char
> +	 * so that after 256 times the counter wraps and the behavior turns
> +	 * lazy again; this to deal with bursty apps that only use FPU for
> +	 * a short time
> +	 */
> +	unsigned char fpu_counter;
>  };
>  
>  #define INIT_THREAD  {						\
> diff --git a/arch/sh/include/asm/processor_64.h b/arch/sh/include/asm/processor_64.h
> index 1cc7d31..eedd4f6 100644
> --- a/arch/sh/include/asm/processor_64.h
> +++ b/arch/sh/include/asm/processor_64.h
> @@ -126,6 +126,16 @@ struct thread_struct {
>  
>  	/* floating point info */
>  	union thread_xstate *xstate;
> +
> +	/*
> +	 * fpu_counter contains the number of consecutive context switches
> +	 * that the FPU is used. If this is over a threshold, the lazy fpu
> +	 * saving becomes unlazy to save the trap. This is an unsigned char
> +	 * so that after 256 times the counter wraps and the behavior turns
> +	 * lazy again; this to deal with bursty apps that only use FPU for
> +	 * a short time
> +	 */
> +	unsigned char fpu_counter;
>  };
>  
>  #define INIT_MMAP \
> diff --git a/arch/sh/kernel/cpu/fpu.c b/arch/sh/kernel/cpu/fpu.c
> index f8f7af5..4e33224 100644
> --- a/arch/sh/kernel/cpu/fpu.c
> +++ b/arch/sh/kernel/cpu/fpu.c
> @@ -44,7 +44,7 @@ void __fpu_state_restore(void)
>  	restore_fpu(tsk);
>  
>  	task_thread_info(tsk)->status |= TS_USEDFPU;
> -	tsk->fpu_counter++;
> +	tsk->thread.fpu_counter++;
>  }
>  
>  void fpu_state_restore(struct pt_regs *regs)
> diff --git a/arch/sh/kernel/process_32.c b/arch/sh/kernel/process_32.c
> index ebd3933..2885fc9 100644
> --- a/arch/sh/kernel/process_32.c
> +++ b/arch/sh/kernel/process_32.c
> @@ -156,7 +156,7 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
>  #endif
>  		ti->addr_limit = KERNEL_DS;
>  		ti->status &= ~TS_USEDFPU;
> -		p->fpu_counter = 0;
> +		p->thread.fpu_counter = 0;
>  		return 0;
>  	}
>  	*childregs = *current_pt_regs();
> @@ -189,7 +189,7 @@ __switch_to(struct task_struct *prev, struct task_struct *next)
>  	unlazy_fpu(prev, task_pt_regs(prev));
>  
>  	/* we're going to use this soon, after a few expensive things */
> -	if (next->fpu_counter > 5)
> +	if (next->thread.fpu_counter > 5)
>  		prefetch(next_t->xstate);
>  
>  #ifdef CONFIG_MMU
> @@ -207,7 +207,7 @@ __switch_to(struct task_struct *prev, struct task_struct *next)
>  	 * restore of the math state immediately to avoid the trap; the
>  	 * chances of needing FPU soon are obviously high now
>  	 */
> -	if (next->fpu_counter > 5)
> +	if (next->thread.fpu_counter > 5)
>  		__fpu_state_restore();
>  
>  	return prev;
>