powerpc: tracing: Add hypervisor call tracepoints
Add hcall_entry and hcall_exit tracepoints. This replaces the inline assembly HCALL_STATS code and converts it to use the new tracepoints. To keep the disabled case as quick as possible, we embed a status word in the TOC so we can get at it with a single load. By doing so we keep the overhead at a minimum. Time taken for a null hcall: No tracepoint code: 135.79 cycles Disabled tracepoints: 137.95 cycles For reference, before this patch enabling HCALL_STATS resulted in a null hcall of 201.44 cycles! Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Anton Blanchard
Paul Mackerras
parent
6795b85c6a
commit
c8cd093a6e
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@ -46,7 +46,7 @@ config DEBUG_STACK_USAGE
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config HCALL_STATS
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bool "Hypervisor call instrumentation"
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depends on PPC_PSERIES && DEBUG_FS
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depends on PPC_PSERIES && DEBUG_FS && TRACEPOINTS
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help
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Adds code to keep track of the number of hypervisor calls made and
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the amount of time spent in hypervisor calls. Wall time spent in
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@ -274,6 +274,8 @@ struct hcall_stats {
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unsigned long num_calls; /* number of calls (on this CPU) */
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unsigned long tb_total; /* total wall time (mftb) of calls. */
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unsigned long purr_total; /* total cpu time (PURR) of calls. */
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unsigned long tb_start;
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unsigned long purr_start;
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};
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#define HCALL_STAT_ARRAY_SIZE ((MAX_HCALL_OPCODE >> 2) + 1)
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@ -76,6 +76,51 @@ TRACE_EVENT(timer_interrupt_exit,
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TP_printk("pt_regs=%p", __entry->regs)
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);
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#ifdef CONFIG_PPC_PSERIES
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extern void hcall_tracepoint_regfunc(void);
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extern void hcall_tracepoint_unregfunc(void);
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TRACE_EVENT_FN(hcall_entry,
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TP_PROTO(unsigned long opcode),
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TP_ARGS(opcode),
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TP_STRUCT__entry(
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__field(unsigned long, opcode)
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),
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TP_fast_assign(
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__entry->opcode = opcode;
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),
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TP_printk("opcode=%lu", __entry->opcode),
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hcall_tracepoint_regfunc, hcall_tracepoint_unregfunc
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);
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TRACE_EVENT_FN(hcall_exit,
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TP_PROTO(unsigned long opcode, unsigned long retval),
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TP_ARGS(opcode, retval),
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TP_STRUCT__entry(
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__field(unsigned long, opcode)
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__field(unsigned long, retval)
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),
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TP_fast_assign(
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__entry->opcode = opcode;
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__entry->retval = retval;
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),
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TP_printk("opcode=%lu retval=%lu", __entry->opcode, __entry->retval),
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hcall_tracepoint_regfunc, hcall_tracepoint_unregfunc
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);
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#endif
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#endif /* _TRACE_POWERPC_H */
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#undef TRACE_INCLUDE_PATH
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@ -14,20 +14,54 @@
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#define STK_PARM(i) (48 + ((i)-3)*8)
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#ifdef CONFIG_HCALL_STATS
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#ifdef CONFIG_TRACEPOINTS
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.section ".toc","aw"
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.globl hcall_tracepoint_refcount
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hcall_tracepoint_refcount:
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.llong 0
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.section ".text"
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/*
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* precall must preserve all registers. use unused STK_PARM()
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* areas to save snapshots and opcode.
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* areas to save snapshots and opcode. We branch around this
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* in early init (eg when populating the MMU hashtable) by using an
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* unconditional cpu feature.
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*/
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#define HCALL_INST_PRECALL \
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std r3,STK_PARM(r3)(r1); /* save opcode */ \
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mftb r0; /* get timebase and */ \
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std r0,STK_PARM(r5)(r1); /* save for later */ \
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BEGIN_FTR_SECTION; \
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mfspr r0,SPRN_PURR; /* get PURR and */ \
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std r0,STK_PARM(r6)(r1); /* save for later */ \
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END_FTR_SECTION_IFSET(CPU_FTR_PURR);
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b 1f; \
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END_FTR_SECTION(0, 1); \
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ld r12,hcall_tracepoint_refcount@toc(r2); \
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cmpdi r12,0; \
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beq+ 1f; \
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mflr r0; \
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std r3,STK_PARM(r3)(r1); \
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std r4,STK_PARM(r4)(r1); \
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std r5,STK_PARM(r5)(r1); \
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std r6,STK_PARM(r6)(r1); \
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std r7,STK_PARM(r7)(r1); \
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std r8,STK_PARM(r8)(r1); \
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std r9,STK_PARM(r9)(r1); \
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std r10,STK_PARM(r10)(r1); \
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std r0,16(r1); \
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stdu r1,-STACK_FRAME_OVERHEAD(r1); \
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bl .__trace_hcall_entry; \
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addi r1,r1,STACK_FRAME_OVERHEAD; \
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ld r0,16(r1); \
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ld r3,STK_PARM(r3)(r1); \
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ld r4,STK_PARM(r4)(r1); \
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ld r5,STK_PARM(r5)(r1); \
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ld r6,STK_PARM(r6)(r1); \
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ld r7,STK_PARM(r7)(r1); \
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ld r8,STK_PARM(r8)(r1); \
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ld r9,STK_PARM(r9)(r1); \
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ld r10,STK_PARM(r10)(r1); \
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mtlr r0; \
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1:
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/*
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* postcall is performed immediately before function return which
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* allows liberal use of volatile registers. We branch around this
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@ -38,40 +72,21 @@ END_FTR_SECTION_IFSET(CPU_FTR_PURR);
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BEGIN_FTR_SECTION; \
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b 1f; \
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END_FTR_SECTION(0, 1); \
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ld r4,STK_PARM(r3)(r1); /* validate opcode */ \
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cmpldi cr7,r4,MAX_HCALL_OPCODE; \
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bgt- cr7,1f; \
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\
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/* get time and PURR snapshots after hcall */ \
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mftb r7; /* timebase after */ \
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BEGIN_FTR_SECTION; \
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mfspr r8,SPRN_PURR; /* PURR after */ \
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ld r6,STK_PARM(r6)(r1); /* PURR before */ \
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subf r6,r6,r8; /* delta */ \
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END_FTR_SECTION_IFSET(CPU_FTR_PURR); \
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ld r5,STK_PARM(r5)(r1); /* timebase before */ \
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subf r5,r5,r7; /* time delta */ \
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\
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/* calculate address of stat structure r4 = opcode */ \
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srdi r4,r4,2; /* index into array */ \
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mulli r4,r4,HCALL_STAT_SIZE; \
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LOAD_REG_ADDR(r7, per_cpu__hcall_stats); \
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add r4,r4,r7; \
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ld r7,PACA_DATA_OFFSET(r13); /* per cpu offset */ \
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add r4,r4,r7; \
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\
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/* update stats */ \
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ld r7,HCALL_STAT_CALLS(r4); /* count */ \
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addi r7,r7,1; \
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std r7,HCALL_STAT_CALLS(r4); \
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ld r7,HCALL_STAT_TB(r4); /* timebase */ \
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add r7,r7,r5; \
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std r7,HCALL_STAT_TB(r4); \
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BEGIN_FTR_SECTION; \
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ld r7,HCALL_STAT_PURR(r4); /* PURR */ \
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add r7,r7,r6; \
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std r7,HCALL_STAT_PURR(r4); \
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END_FTR_SECTION_IFSET(CPU_FTR_PURR); \
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ld r12,hcall_tracepoint_refcount@toc(r2); \
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cmpdi r12,0; \
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beq+ 1f; \
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mflr r0; \
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ld r6,STK_PARM(r3)(r1); \
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std r3,STK_PARM(r3)(r1); \
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mr r4,r3; \
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mr r3,r6; \
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std r0,16(r1); \
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stdu r1,-STACK_FRAME_OVERHEAD(r1); \
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bl .__trace_hcall_exit; \
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addi r1,r1,STACK_FRAME_OVERHEAD; \
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ld r0,16(r1); \
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ld r3,STK_PARM(r3)(r1); \
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mtlr r0; \
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1:
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#else
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#define HCALL_INST_PRECALL
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@ -26,6 +26,7 @@
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#include <asm/hvcall.h>
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#include <asm/firmware.h>
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#include <asm/cputable.h>
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#include <asm/trace.h>
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DEFINE_PER_CPU(struct hcall_stats[HCALL_STAT_ARRAY_SIZE], hcall_stats);
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@ -100,6 +101,34 @@ static const struct file_operations hcall_inst_seq_fops = {
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#define HCALL_ROOT_DIR "hcall_inst"
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#define CPU_NAME_BUF_SIZE 32
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static void probe_hcall_entry(unsigned long opcode)
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{
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struct hcall_stats *h;
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if (opcode > MAX_HCALL_OPCODE)
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return;
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h = &get_cpu_var(hcall_stats)[opcode / 4];
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h->tb_start = mftb();
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h->purr_start = mfspr(SPRN_PURR);
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}
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static void probe_hcall_exit(unsigned long opcode, unsigned long retval)
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{
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struct hcall_stats *h;
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if (opcode > MAX_HCALL_OPCODE)
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return;
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h = &__get_cpu_var(hcall_stats)[opcode / 4];
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h->num_calls++;
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h->tb_total = mftb() - h->tb_start;
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h->purr_total = mfspr(SPRN_PURR) - h->purr_start;
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put_cpu_var(hcall_stats);
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}
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static int __init hcall_inst_init(void)
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{
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struct dentry *hcall_root;
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@ -110,6 +139,14 @@ static int __init hcall_inst_init(void)
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if (!firmware_has_feature(FW_FEATURE_LPAR))
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return 0;
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if (register_trace_hcall_entry(probe_hcall_entry))
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return -EINVAL;
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if (register_trace_hcall_exit(probe_hcall_exit)) {
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unregister_trace_hcall_entry(probe_hcall_entry);
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return -EINVAL;
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}
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hcall_root = debugfs_create_dir(HCALL_ROOT_DIR, NULL);
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if (!hcall_root)
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return -ENOMEM;
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@ -39,6 +39,7 @@
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#include <asm/cputable.h>
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#include <asm/udbg.h>
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#include <asm/smp.h>
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#include <asm/trace.h>
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#include "plpar_wrappers.h"
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#include "pseries.h"
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@ -661,3 +662,34 @@ void arch_free_page(struct page *page, int order)
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EXPORT_SYMBOL(arch_free_page);
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#endif
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#ifdef CONFIG_TRACEPOINTS
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/*
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* We optimise our hcall path by placing hcall_tracepoint_refcount
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* directly in the TOC so we can check if the hcall tracepoints are
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* enabled via a single load.
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*/
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/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
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extern long hcall_tracepoint_refcount;
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void hcall_tracepoint_regfunc(void)
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{
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hcall_tracepoint_refcount++;
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}
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void hcall_tracepoint_unregfunc(void)
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{
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hcall_tracepoint_refcount--;
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}
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void __trace_hcall_entry(unsigned long opcode)
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{
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trace_hcall_entry(opcode);
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}
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void __trace_hcall_exit(long opcode, unsigned long retval)
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{
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trace_hcall_exit(opcode, retval);
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}
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#endif
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