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x86, fpu: lazy allocation of FPU area - v5

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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: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Suresh Siddha 2008-03-10 15:28:05 -07:00 committed by Ingo Molnar
parent 61c4628b53
commit aa283f4927
8 changed files with 91 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
arch/x86/kernel/i387.c
View File

@ -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) {

28
arch/x86/kernel/process.c
View File

@ -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_xstate(struct task_struct *tsk)
{
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)
{
kmem_cache_free(task_xstate_cachep, ti->task->thread.xstate);
ti->task->thread.xstate = NULL;
free_thread_xstate(ti->task);
free_pages((unsigned long)(ti), get_order(THREAD_SIZE));
}

4
arch/x86/kernel/process_32.c
View File

@ -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);

4
arch/x86/kernel/process_64.c
View File

@ -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);

17
arch/x86/kernel/traps_32.c
View File

@ -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++;

19
arch/x86/kernel/traps_64.c
View File

@ -1124,10 +1124,23 @@ asmlinkage void __attribute__((weak)) mce_threshold_interrupt(void)
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()) {
local_irq_enable();
/*
* does a slab alloc which can sleep
*/
if (init_fpu(me)) {
/*
* ran out of memory!
*/
do_group_exit(SIGKILL);
return;
}
local_irq_disable();
}
clts(); /* Allow maths ops (or we recurse) */
restore_fpu_checking(&me->thread.xstate->fxsave);
task_thread_info(me)->status |= TS_USEDFPU;
me->fpu_counter++;

2
include/asm-x86/i387.h
View File

@ -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);

2
include/asm-x86/processor.h
View File

@ -366,6 +366,8 @@ DECLARE_PER_CPU(struct orig_ist, orig_ist);
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;