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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
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38
arch/x86/kernel/i387.c
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@@ -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) {