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Message-ID: <524AA4FD.6070001@synopsys.com>
Date: Tue, 1 Oct 2013 16:03:33 +0530
From: Vineet Gupta <Vineet.Gupta1@...opsys.com>
To: Paul Mundt <lethal@...ux-sh.org>, <linux-sh@...r.kernel.org>
CC: Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
<linux-arch@...r.kernel.org>, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH REBASED 1/3] sh: Move fpu_counter into ARCH specific
thread_struct
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@...opsys.com>
> Cc: Paul Mundt <lethal@...ux-sh.org>
> Cc: Michel Lespinasse <walken@...gle.com>
> Cc: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Jesper Nilsson <jesper.nilsson@...s.com>
> Cc: Chris Metcalf <cmetcalf@...era.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-arch@...r.kernel.org
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: linux-sh@...r.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;
>
--
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