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: 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>
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index baf632b..db6839b 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -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 @@
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 @@
* 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 @@
* 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 @@
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 @@
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 @@
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 @@
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) {
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index ead24ef..0e613e7 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -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));
}
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 3890a5d..7adad08 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -521,6 +521,10 @@
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);
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index b795e83..891af1a 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -533,6 +533,10 @@
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);
diff --git a/arch/x86/kernel/traps_32.c b/arch/x86/kernel/traps_32.c
index 8d136a7..471e694 100644
--- a/arch/x86/kernel/traps_32.c
+++ b/arch/x86/kernel/traps_32.c
@@ -1148,9 +1148,22 @@
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++;
diff --git a/arch/x86/kernel/traps_64.c b/arch/x86/kernel/traps_64.c
index dc0cb49..adff76e 100644
--- a/arch/x86/kernel/traps_64.c
+++ b/arch/x86/kernel/traps_64.c
@@ -1124,10 +1124,23 @@
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++;
