LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Bastien ROUCARIES <roucaries.bastien@gmail.com>
To: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: mingo@elte.hu, hpa@zytor.com, tglx@linutronix.de,
	andi@firstfloor.org, hch@infradead.org,
	linux-kernel@vger.kernel.org,
	Arjan van de Ven <arjan@linux.intel.com>
Subject: Re: [patch 2/2] x86, fpu: lazy allocation of FPU area - v4
Date: Thu, 6 Mar 2008 13:40:07 +0100	[thread overview]
Message-ID: <200803061340.09904.roucaries.bastien@gmail.com> (raw)
In-Reply-To: <20080304234003.752305000@linux-os.sc.intel.com>

Le mercredi 5 mars 2008, Suresh Siddha a écrit :
> Only allocate the FPU area when the application actually uses FPU, i.e., in
> the first lazy FPU trap. This could save memory for non-fpu using apps.
>
> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
> Cc: Arjan van de Ven <arjan@linux.intel.com>
> ---
> v4: Handles the kmem_cache_alloc() failures.
> v3: Fixed the non-atomic calling sequence in atomic context.
> v2: Ported to x86.git#testing with some name changes.
> ---
>
> Index: linux-2.6-x86/arch/x86/kernel/i387.c
> ===================================================================
> --- linux-2.6-x86.orig/arch/x86/kernel/i387.c	2008-03-04 15:31:56.000000000
> -0800 +++ linux-2.6-x86/arch/x86/kernel/i387.c	2008-03-04
> 15:31:57.000000000 -0800 @@ -9,7 +9,6 @@
>  #include <linux/sched.h>
>  #include <linux/module.h>
>  #include <linux/regset.h>
> -#include <linux/bootmem.h>
>  #include <asm/processor.h>
>  #include <asm/i387.h>
>  #include <asm/math_emu.h>
> @@ -67,7 +66,6 @@
>  	else
>  		xstate_size = sizeof(struct i387_fsave_struct);
>  #endif
> -	init_task.thread.xstate = alloc_bootmem(xstate_size);
>  }
>
>  #ifdef CONFIG_X86_64
> @@ -97,12 +95,22 @@
>   * value at reset if we support XMM instructions and then
>   * remeber the current task has used the FPU.
>   */
> -void init_fpu(struct task_struct *tsk)
> +int init_fpu(struct task_struct *tsk)
>  {
>  	if (tsk_used_math(tsk)) {
>  		if (tsk == current)
>  			unlazy_fpu(tsk);
> -		return;
> +		return 0;
> +	}
> +
> +	/*
> +	 * Memory allocation at the first usage of the FPU and other state.
> +	 */
> +	if (!tsk->thread.xstate) {
> +		tsk->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
> +						      GFP_KERNEL);
> +		if (!tsk->thread.xstate)
> +			return -ENOMEM;
>  	}
>
>  	if (cpu_has_fxsr) {
> @@ -124,6 +132,7 @@
>  	 * Only the device not available exception or ptrace can call init_fpu.
>  	 */
>  	set_stopped_child_used_math(tsk);
> +	return 0;
>  }
>
>  int fpregs_active(struct task_struct *target, const struct user_regset
> *regset) @@ -140,10 +149,14 @@
>  		unsigned int pos, unsigned int count,
>  		void *kbuf, void __user *ubuf)
>  {
> +	int ret;
> +
>  	if (!cpu_has_fxsr)
>  		return -ENODEV;
>
> -	init_fpu(target);
> +	ret = init_fpu(target);
> +	if (ret)
> +		return ret;
>
>  	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
>  				   &target->thread.xstate->fxsave, 0, -1);
> @@ -158,7 +171,10 @@
>  	if (!cpu_has_fxsr)
>  		return -ENODEV;
>
> -	init_fpu(target);
> +	ret = init_fpu(target);
> +	if (ret)
> +		return ret;
> +
>  	set_stopped_child_used_math(target);
>
>  	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
> @@ -314,11 +330,14 @@
>  	       void *kbuf, void __user *ubuf)
>  {
>  	struct user_i387_ia32_struct env;
> +	int ret;
>
>  	if (!HAVE_HWFP)
>  		return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
>
> -	init_fpu(target);
> +	ret = init_fpu(target);
> +	if (ret)
> +		return ret;
>
>  	if (!cpu_has_fxsr)
>  		return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
> @@ -343,7 +362,10 @@
>  	if (!HAVE_HWFP)
>  		return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
>
> -	init_fpu(target);
> +	ret = init_fpu(target);
> +	if (ret)
> +		return ret;
> +
>  	set_stopped_child_used_math(target);
>
>  	if (!cpu_has_fxsr)
> Index: linux-2.6-x86/arch/x86/kernel/process.c
> ===================================================================
> --- linux-2.6-x86.orig/arch/x86/kernel/process.c	2008-03-04
> 15:31:56.000000000 -0800 +++
> linux-2.6-x86/arch/x86/kernel/process.c	2008-03-04 15:32:23.000000000 -0800
> @@ -5,24 +5,34 @@
>  #include <linux/slab.h>
>  #include <linux/sched.h>
>
> -static struct kmem_cache *task_xstate_cachep;
> +struct kmem_cache *task_xstate_cachep;
>
>  int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
>  {
>  	*dst = *src;
> -	dst->thread.xstate = kmem_cache_alloc(task_xstate_cachep, GFP_KERNEL);
> -	if (!dst->thread.xstate)
> -		return -ENOMEM;
> -	WARN_ON((unsigned long)dst->thread.xstate & 15);
> -	memcpy(dst->thread.xstate, src->thread.xstate, xstate_size);
> +	if (src->thread.xstate) {
> +		dst->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
> +						      GFP_KERNEL);
> +		if (!dst->thread.xstate)
> +			return -ENOMEM;
> +		WARN_ON((unsigned long)dst->thread.xstate & 15);
> +		memcpy(dst->thread.xstate, src->thread.xstate, xstate_size);
> +	}
>  	return 0;
>  }
>
> -void free_thread_info(struct thread_info *ti)
> +void free_thread_xstate(struct task_struct *tsk)
>  {
> -	kmem_cache_free(task_xstate_cachep, ti->task->thread.xstate);
> -	ti->task->thread.xstate = NULL;
> +	if (tsk->thread.xstate) {
> +		kmem_cache_free(task_xstate_cachep, tsk->thread.xstate);
> +		tsk->thread.xstate = NULL;
> +	}
> +}
> +
>
> +void free_thread_info(struct thread_info *ti)
> +{
> +	free_thread_xstate(ti->task);
>  	free_pages((unsigned long)(ti), get_order(THREAD_SIZE));
>  }
>
> Index: linux-2.6-x86/include/asm-x86/processor.h
> ===================================================================
> --- linux-2.6-x86.orig/include/asm-x86/processor.h	2008-03-04
> 15:31:56.000000000 -0800 +++
> linux-2.6-x86/include/asm-x86/processor.h	2008-03-04 15:31:57.000000000
> -0800 @@ -354,6 +354,8 @@
>
>  extern void print_cpu_info(struct cpuinfo_x86 *);
>  extern unsigned int xstate_size;
> +extern void free_thread_xstate(struct task_struct *);
> +extern struct kmem_cache *task_xstate_cachep;
>  extern void init_scattered_cpuid_features(struct cpuinfo_x86 *c);
>  extern unsigned int init_intel_cacheinfo(struct cpuinfo_x86 *c);
>  extern unsigned short num_cache_leaves;
> Index: linux-2.6-x86/arch/x86/kernel/process_32.c
> ===================================================================
> --- linux-2.6-x86.orig/arch/x86/kernel/process_32.c	2008-03-04
> 15:31:56.000000000 -0800 +++
> linux-2.6-x86/arch/x86/kernel/process_32.c	2008-03-04 15:31:57.000000000
> -0800 @@ -524,6 +524,10 @@
>  	regs->cs		= __USER_CS;
>  	regs->ip		= new_ip;
>  	regs->sp		= new_sp;
> +	/*
> +	 * Free the old FP and other extended state
> +	 */
> +	free_thread_xstate(current);
>  }
>  EXPORT_SYMBOL_GPL(start_thread);
>
> Index: linux-2.6-x86/arch/x86/kernel/process_64.c
> ===================================================================
> --- linux-2.6-x86.orig/arch/x86/kernel/process_64.c	2008-03-04
> 15:31:56.000000000 -0800 +++
> linux-2.6-x86/arch/x86/kernel/process_64.c	2008-03-04 15:31:57.000000000
> -0800 @@ -552,6 +552,10 @@
>  	regs->ss		= __USER_DS;
>  	regs->flags		= 0x200;
>  	set_fs(USER_DS);
> +	/*
> +	 * Free the old FP and other extended state
> +	 */
> +	free_thread_xstate(current);
>  }
>  EXPORT_SYMBOL_GPL(start_thread);
>
> Index: linux-2.6-x86/arch/x86/kernel/traps_32.c
> ===================================================================
> --- linux-2.6-x86.orig/arch/x86/kernel/traps_32.c	2008-03-04
> 15:31:56.000000000 -0800 +++
> linux-2.6-x86/arch/x86/kernel/traps_32.c	2008-03-04 15:31:57.000000000
> -0800 @@ -1168,9 +1168,23 @@
>  	struct thread_info *thread = current_thread_info();
>  	struct task_struct *tsk = thread->task;
>
> +	if (!tsk_used_math(tsk)) {
> +#ifdef CONFIG_PREEMPT
> +		local_irq_enable();
> +#endif
> +		/*
> +		 * does a slab alloc which can sleep
> +		 */
> +		if (init_fpu(tsk)) {
> +			force_sig(SIGSEGV, tsk);

May be SIGBUS will be better here?


> +			return;
> +		}
> +#ifdef CONFIG_PREEMPT
> +		local_irq_disable();
> +#endif
> +	}
> +
>  	clts();				/* Allow maths ops (or we recurse) */
> -	if (!tsk_used_math(tsk))
> -		init_fpu(tsk);
>  	restore_fpu(tsk);
>  	thread->status |= TS_USEDFPU;	/* So we fnsave on switch_to() */
>  	tsk->fpu_counter++;
> Index: linux-2.6-x86/arch/x86/kernel/traps_64.c
> ===================================================================
> --- linux-2.6-x86.orig/arch/x86/kernel/traps_64.c	2008-03-04
> 15:31:56.000000000 -0800 +++
> linux-2.6-x86/arch/x86/kernel/traps_64.c	2008-03-04 15:31:57.000000000
> -0800 @@ -1117,10 +1117,15 @@
>  asmlinkage void math_state_restore(void)
>  {
>  	struct task_struct *me = current;
> -	clts();			/* Allow maths ops (or we recurse) */
>
> -	if (!used_math())
> -		init_fpu(me);
> +	if (!used_math()) {
> +		if (init_fpu(me)) {
> +			force_sig(SIGSEGV, me);
> +			return;
> +		}
> +	}
> +
> +	clts();			/* Allow maths ops (or we recurse) */
>  	restore_fpu_checking(&me->thread.xstate->fxsave);
>  	task_thread_info(me)->status |= TS_USEDFPU;
>  	me->fpu_counter++;
> Index: linux-2.6-x86/include/asm-x86/i387.h
> ===================================================================
> --- linux-2.6-x86.orig/include/asm-x86/i387.h	2008-03-04 15:31:56.000000000
> -0800 +++ linux-2.6-x86/include/asm-x86/i387.h	2008-03-04
> 15:31:57.000000000 -0800 @@ -21,7 +21,7 @@
>
>  extern void fpu_init(void);
>  extern void mxcsr_feature_mask_init(void);
> -extern void init_fpu(struct task_struct *child);
> +extern int init_fpu(struct task_struct *child);
>  extern asmlinkage void math_state_restore(void);
>  extern void init_thread_xstate(void);


Regards
-- 

"ROUCARIES Bastien"


  reply	other threads:[~2008-03-06 12:36 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-04 23:37 [patch 1/2] x86, fpu: split FPU state from task struct " Suresh Siddha
2008-03-04 23:37 ` [patch 2/2] x86, fpu: lazy allocation of FPU area " Suresh Siddha
2008-03-06 12:40   ` Bastien ROUCARIES [this message]
2008-03-06 12:17 ` [patch 1/2] x86, fpu: split FPU state from task struct " Ingo Molnar
2008-03-06 15:18   ` Ingo Molnar
2008-03-06 19:03     ` Suresh Siddha
2008-03-06 19:19       ` Ingo Molnar

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=200803061340.09904.roucaries.bastien@gmail.com \
    --to=roucaries.bastien@gmail.com \
    --cc=andi@firstfloor.org \
    --cc=arjan@linux.intel.com \
    --cc=hch@infradead.org \
    --cc=hpa@zytor.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@elte.hu \
    --cc=suresh.b.siddha@intel.com \
    --cc=tglx@linutronix.de \
    --subject='Re: [patch 2/2] x86, fpu: lazy allocation of FPU area - v4' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).