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/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++;