Commit aa283f49 authored by Suresh Siddha's avatar Suresh Siddha Committed by Ingo Molnar
Browse files

x86, fpu: lazy allocation of FPU area - v5 



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.

for example: on my system after boot, there are around 300 processes, with
only 17 using FPU.

Signed-off-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 61c4628b

arch/x86/kernel/i387.c

+30 −8
Original line number Diff line number Diff line
@@ -8,7 +8,6 @@ 
#include <linux/module.h>

#include <linux/regset.h>

#include <linux/sched.h>

#include <linux/bootmem.h>



#include <asm/sigcontext.h>

#include <asm/processor.h>
@@ -63,7 +62,6 @@ void __init init_thread_xstate(void) 
	else

		xstate_size = sizeof(struct i387_fsave_struct);

#endif

	init_task.thread.xstate = alloc_bootmem(xstate_size);

}



#ifdef CONFIG_X86_64
@@ -93,12 +91,22 @@ void __cpuinit fpu_init(void) 
 * 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) {
@@ -120,6 +128,7 @@ void init_fpu(struct task_struct *tsk) 
	 * 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)
@@ -136,10 +145,14 @@ int xfpregs_get(struct task_struct *target, const struct user_regset *regset, 
		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);
@@ -154,7 +167,10 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset, 
	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,
@@ -312,11 +328,14 @@ int fpregs_get(struct task_struct *target, const struct user_regset *regset, 
	       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,
@@ -344,7 +363,10 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset, 
	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) {

arch/x86/kernel/process.c

+19 −9
Original line number Diff line number Diff line
@@ -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 (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));

}

arch/x86/kernel/process_32.c

+4 −0
Original line number Diff line number Diff line
@@ -521,6 +521,10 @@ start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) 
	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);

arch/x86/kernel/process_64.c

+4 −0
Original line number Diff line number Diff line
@@ -533,6 +533,10 @@ start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) 
	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);

arch/x86/kernel/traps_32.c

+15 −2
Original line number Diff line number Diff line
@@ -1148,9 +1148,22 @@ asmlinkage void math_state_restore(void) 
	struct thread_info *thread = current_thread_info();

	struct task_struct *tsk = thread->task;



	if (!tsk_used_math(tsk)) {

		local_irq_enable();

		/*

		 * does a slab alloc which can sleep

		 */

		if (init_fpu(tsk)) {

			/*

			 * ran out of memory!

			 */

			do_group_exit(SIGKILL);

			return;

		}

		local_irq_disable();

	}



	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++;

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