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Commit cb2c9b27 authored by Anton Blanchard's avatar Anton Blanchard Committed by Paul Mackerras
Browse files

[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: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent 47f78a49

arch/powerpc/kernel/head_64.S

+2 −10
Original line number Diff line number Diff line
@@ -319,7 +319,6 @@ exception_marker: 
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##_pSeries: \ 
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: \ 
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: \ 
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 @@ __start_interrupts: 
_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 @@ END_FTR_SECTION_IFCLR(CPU_FTR_SLB) 
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 @@ data_access_slb_pSeries: 
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 @@ instruction_access_slb_pSeries: 
	.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 @@ slb_miss_user_pseries: 
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 @@ system_reset_fwnmi: 
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 @@ unrecov_fer: 
	.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 @@ hardware_interrupt_common: 
	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

arch/powerpc/kernel/process.c

+32 −0
Original line number Diff line number Diff line
@@ -888,3 +888,35 @@ void dump_stack(void) 
	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

arch/powerpc/platforms/iseries/setup.c

+1 −0
Original line number Diff line number Diff line
@@ -648,6 +648,7 @@ static void yield_shared_processor(void) 
	 * 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();

}

include/asm-powerpc/reg.h

+3 −30
Original line number Diff line number Diff line
@@ -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 */

include/asm-powerpc/thread_info.h

+2 −2
Original line number Diff line number Diff line
@@ -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)