sh: add sleazy FPU optimization

[net-next-2.6.git] / arch / sh / kernel / process_32.c

diff --git a/arch/sh/kernel/process_32.c b/arch/sh/kernel/process_32.c
index 0673c4746be3996f58a33de506ca6e664284a044..aff5fe02e393c417a3c8646447bf0d7fd8ef504e 100644 (file)
--- a/arch/sh/kernel/process_32.c
+++ b/arch/sh/kernel/process_32.c
@@ -288,8 +288,14 @@ static void ubc_set_tracing(int asid, unsigned long pc)
 __notrace_funcgraph struct task_struct *
 __switch_to(struct task_struct *prev, struct task_struct *next)
 {
+       struct thread_struct *next_t = &next->thread;
+
 #if defined(CONFIG_SH_FPU)
        unlazy_fpu(prev, task_pt_regs(prev));
+
+       /* we're going to use this soon, after a few expensive things */
+       if (next->fpu_counter > 5)
+               prefetch(&next_t->fpu.hard);
 #endif
 
 #ifdef CONFIG_MMU
@@ -321,6 +327,16 @@ __switch_to(struct task_struct *prev, struct task_struct *next)
 #endif
        }
 
+#if defined(CONFIG_SH_FPU)
+       /* If the task has used fpu the last 5 timeslices, just do a full
+        * restore of the math state immediately to avoid the trap; the
+        * chances of needing FPU soon are obviously high now
+        */
+       if (next->fpu_counter > 5) {
+               fpu_state_restore(task_pt_regs(next));
+       }
+#endif
+
        return prev;
 }