[PATCH] powerpc: Fix runlatch performance issues

The runlatch SPR can take a lot of time to write. My original runlatch
code would set it on every exception entry even though most of the time
this was not required. It would also continually set it in the idle
loop, which is an issue on an SMT capable processor.

Now we cache the runlatch value in a threadinfo bit, and only check for
it in decrementer and hardware interrupt exceptions as well as the idle
loop. Boot on POWER3, POWER5 and iseries, and compile tested on pmac32.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 5 insertions, 32 deletions

diff --git a/include/asm-powerpc/reg.h b/include/asm-powerpc/reg.h
index 12ecc9b9f285..72bfe3af0460 100644
--- a/include/asm-powerpc/reg.h
+++ b/include/asm-powerpc/reg.h
@@ -615,27 +615,9 @@
 #define proc_trap()     asm volatile("trap")
 
 #ifdef CONFIG_PPC64
-static inline void ppc64_runlatch_on(void)
-{
-        unsigned long ctrl;
-
-        if (cpu_has_feature(CPU_FTR_CTRL)) {
-                ctrl = mfspr(SPRN_CTRLF);
-                ctrl |= CTRL_RUNLATCH;
-                mtspr(SPRN_CTRLT, ctrl);
-        }
-}
-
-static inline void ppc64_runlatch_off(void)
-{
-        unsigned long ctrl;
-
-        if (cpu_has_feature(CPU_FTR_CTRL)) {
-                ctrl = mfspr(SPRN_CTRLF);
-                ctrl &= ~CTRL_RUNLATCH;
-                mtspr(SPRN_CTRLT, ctrl);
-        }
-}
+
+extern void ppc64_runlatch_on(void);
+extern void ppc64_runlatch_off(void);
 
 extern unsigned long scom970_read(unsigned int address);
 extern void scom970_write(unsigned int address, unsigned long value);
@@ -645,15 +627,6 @@ extern void scom970_write(unsigned int address, unsigned long value);
 #define __get_SP()      ({unsigned long sp; \
                         asm volatile("mr %0,1": "=r" (sp)); sp;})
 
-#else /* __ASSEMBLY__ */
-
-#define RUNLATCH_ON(REG)                        \
-BEGIN_FTR_SECTION                               \
-        mfspr   (REG),SPRN_CTRLF;               \
-        ori     (REG),(REG),CTRL_RUNLATCH;      \
-        mtspr   SPRN_CTRLT,(REG);               \
-END_FTR_SECTION_IFSET(CPU_FTR_CTRL)
-
 #endif /* __ASSEMBLY__ */
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_REG_H */
diff --git a/include/asm-powerpc/thread_info.h b/include/asm-powerpc/thread_info.h
index c044ec16a879..237fc2b72974 100644
--- a/include/asm-powerpc/thread_info.h
+++ b/include/asm-powerpc/thread_info.h
@@ -113,7 +113,7 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_POLLING_NRFLAG      4       /* true if poll_idle() is polling
                                            TIF_NEED_RESCHED */
 #define TIF_32BIT               5       /* 32 bit binary */
-/* #define SPARE                6 */
+#define TIF_RUNLATCH            6       /* Is the runlatch enabled? */
 #define TIF_ABI_PENDING         7       /* 32/64 bit switch needed */
 #define TIF_SYSCALL_AUDIT       8       /* syscall auditing active */
 #define TIF_SINGLESTEP          9       /* singlestepping active */
@@ -131,7 +131,7 @@ static inline struct thread_info *current_thread_info(void)
 #define _TIF_NEED_RESCHED       (1<<TIF_NEED_RESCHED)
 #define _TIF_POLLING_NRFLAG     (1<<TIF_POLLING_NRFLAG)
 #define _TIF_32BIT              (1<<TIF_32BIT)
-/* #define _SPARE               (1<<SPARE) */
+#define _TIF_RUNLATCH           (1<<TIF_RUNLATCH)
 #define _TIF_ABI_PENDING        (1<<TIF_ABI_PENDING)
 #define _TIF_SYSCALL_AUDIT      (1<<TIF_SYSCALL_AUDIT)
 #define _TIF_SINGLESTEP         (1<<TIF_SINGLESTEP)