[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>
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 2b03a09..bb845ee 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -319,7 +319,6 @@
label##_pSeries: \
HMT_MEDIUM; \
mtspr SPRN_SPRG1,r13; /* save r13 */ \
- RUNLATCH_ON(r13); \
EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, label##_common)
#define STD_EXCEPTION_ISERIES(n, label, area) \
@@ -327,7 +326,6 @@
label##_iSeries: \
HMT_MEDIUM; \
mtspr SPRN_SPRG1,r13; /* save r13 */ \
- RUNLATCH_ON(r13); \
EXCEPTION_PROLOG_ISERIES_1(area); \
EXCEPTION_PROLOG_ISERIES_2; \
b label##_common
@@ -337,7 +335,6 @@
label##_iSeries: \
HMT_MEDIUM; \
mtspr SPRN_SPRG1,r13; /* save r13 */ \
- RUNLATCH_ON(r13); \
EXCEPTION_PROLOG_ISERIES_1(PACA_EXGEN); \
lbz r10,PACAPROCENABLED(r13); \
cmpwi 0,r10,0; \
@@ -390,6 +387,7 @@
label##_common: \
EXCEPTION_PROLOG_COMMON(trap, PACA_EXGEN); \
DISABLE_INTS; \
+ bl .ppc64_runlatch_on; \
addi r3,r1,STACK_FRAME_OVERHEAD; \
bl hdlr; \
b .ret_from_except_lite
@@ -407,7 +405,6 @@
_machine_check_pSeries:
HMT_MEDIUM
mtspr SPRN_SPRG1,r13 /* save r13 */
- RUNLATCH_ON(r13)
EXCEPTION_PROLOG_PSERIES(PACA_EXMC, machine_check_common)
. = 0x300
@@ -434,7 +431,6 @@
data_access_slb_pSeries:
HMT_MEDIUM
mtspr SPRN_SPRG1,r13
- RUNLATCH_ON(r13)
mfspr r13,SPRN_SPRG3 /* get paca address into r13 */
std r3,PACA_EXSLB+EX_R3(r13)
mfspr r3,SPRN_DAR
@@ -460,7 +456,6 @@
instruction_access_slb_pSeries:
HMT_MEDIUM
mtspr SPRN_SPRG1,r13
- RUNLATCH_ON(r13)
mfspr r13,SPRN_SPRG3 /* get paca address into r13 */
std r3,PACA_EXSLB+EX_R3(r13)
mfspr r3,SPRN_SRR0 /* SRR0 is faulting address */
@@ -491,7 +486,6 @@
.globl system_call_pSeries
system_call_pSeries:
HMT_MEDIUM
- RUNLATCH_ON(r9)
mr r9,r13
mfmsr r10
mfspr r13,SPRN_SPRG3
@@ -575,7 +569,6 @@
system_reset_fwnmi:
HMT_MEDIUM
mtspr SPRN_SPRG1,r13 /* save r13 */
- RUNLATCH_ON(r13)
EXCEPTION_PROLOG_PSERIES(PACA_EXGEN, system_reset_common)
.globl machine_check_fwnmi
@@ -583,7 +576,6 @@
machine_check_fwnmi:
HMT_MEDIUM
mtspr SPRN_SPRG1,r13 /* save r13 */
- RUNLATCH_ON(r13)
EXCEPTION_PROLOG_PSERIES(PACA_EXMC, machine_check_common)
#ifdef CONFIG_PPC_ISERIES
@@ -894,7 +886,6 @@
.align 7
.globl data_access_common
data_access_common:
- RUNLATCH_ON(r10) /* It wont fit in the 0x300 handler */
mfspr r10,SPRN_DAR
std r10,PACA_EXGEN+EX_DAR(r13)
mfspr r10,SPRN_DSISR
@@ -1042,6 +1033,7 @@
EXCEPTION_PROLOG_COMMON(0x500, PACA_EXGEN)
hardware_interrupt_entry:
DISABLE_INTS
+ bl .ppc64_runlatch_on
addi r3,r1,STACK_FRAME_OVERHEAD
bl .do_IRQ
b .ret_from_except_lite
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 5770399..c225cf1 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -888,3 +888,35 @@
show_stack(current, NULL);
}
EXPORT_SYMBOL(dump_stack);
+
+#ifdef CONFIG_PPC64
+void ppc64_runlatch_on(void)
+{
+ unsigned long ctrl;
+
+ if (cpu_has_feature(CPU_FTR_CTRL) && !test_thread_flag(TIF_RUNLATCH)) {
+ HMT_medium();
+
+ ctrl = mfspr(SPRN_CTRLF);
+ ctrl |= CTRL_RUNLATCH;
+ mtspr(SPRN_CTRLT, ctrl);
+
+ set_thread_flag(TIF_RUNLATCH);
+ }
+}
+
+void ppc64_runlatch_off(void)
+{
+ unsigned long ctrl;
+
+ if (cpu_has_feature(CPU_FTR_CTRL) && test_thread_flag(TIF_RUNLATCH)) {
+ HMT_medium();
+
+ clear_thread_flag(TIF_RUNLATCH);
+
+ ctrl = mfspr(SPRN_CTRLF);
+ ctrl &= ~CTRL_RUNLATCH;
+ mtspr(SPRN_CTRLT, ctrl);
+ }
+}
+#endif
diff --git a/arch/powerpc/platforms/iseries/setup.c b/arch/powerpc/platforms/iseries/setup.c
index 3f87901..3ecc4a6 100644
--- a/arch/powerpc/platforms/iseries/setup.c
+++ b/arch/powerpc/platforms/iseries/setup.c
@@ -648,6 +648,7 @@
* here and let the timer_interrupt code sort out the actual time.
*/
get_lppaca()->int_dword.fields.decr_int = 1;
+ ppc64_runlatch_on();
process_iSeries_events();
}
