From: Like Xu <likexu@xxxxxxxxxxx> Most invocation of start_event() and measure() first sets evt.count=0. Instead of forcing each caller to ensure count is zeroed, optimize the count to zero during start_event(), then drop all of the manual zeroing. Accumulating counts can be handled by reading the current count before start_event(), and doing something like stuffing a high count to test an edge case could be handled by an inner helper, __start_event(). For overflow, just open code measure() for that one-off case. Requiring callers to zero out a field in most common cases isn't exactly flexible. Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx> Signed-off-by: Like Xu <likexu@xxxxxxxxxxx> --- x86/pmu.c | 31 ++++++++++++++++--------------- 1 file changed, 16 insertions(+), 15 deletions(-) diff --git a/x86/pmu.c b/x86/pmu.c index d59baf1..817b4d0 100644 --- a/x86/pmu.c +++ b/x86/pmu.c @@ -137,9 +137,9 @@ static void global_disable(pmu_counter_t *cnt) ~(1ull << cnt->idx)); } - -static void start_event(pmu_counter_t *evt) +static void __start_event(pmu_counter_t *evt, uint64_t count) { + evt->count = count; wrmsr(evt->ctr, evt->count); if (is_gp(evt)) wrmsr(MSR_P6_EVNTSEL0 + event_to_global_idx(evt), @@ -162,6 +162,11 @@ static void start_event(pmu_counter_t *evt) apic_write(APIC_LVTPC, PC_VECTOR); } +static void start_event(pmu_counter_t *evt) +{ + __start_event(evt, 0); +} + static void stop_event(pmu_counter_t *evt) { global_disable(evt); @@ -186,6 +191,13 @@ static void measure(pmu_counter_t *evt, int count) stop_event(&evt[i]); } +static void __measure(pmu_counter_t *evt, uint64_t count) +{ + __start_event(evt, count); + loop(); + stop_event(evt); +} + static bool verify_event(uint64_t count, struct pmu_event *e) { // printf("%d <= %ld <= %d\n", e->min, count, e->max); @@ -208,7 +220,6 @@ static void check_gp_counter(struct pmu_event *evt) int i; for (i = 0; i < nr_gp_counters; i++, cnt.ctr++) { - cnt.count = 0; measure(&cnt, 1); report(verify_event(cnt.count, evt), "%s-%d", evt->name, i); } @@ -235,7 +246,6 @@ static void check_fixed_counters(void) int i; for (i = 0; i < nr_fixed_counters; i++) { - cnt.count = 0; cnt.ctr = fixed_events[i].unit_sel; measure(&cnt, 1); report(verify_event(cnt.count, &fixed_events[i]), "fixed-%d", i); @@ -253,14 +263,12 @@ static void check_counters_many(void) if (!pmu_gp_counter_is_available(i)) continue; - cnt[n].count = 0; cnt[n].ctr = gp_counter_base + n; cnt[n].config = EVNTSEL_OS | EVNTSEL_USR | gp_events[i % ARRAY_SIZE(gp_events)].unit_sel; n++; } for (i = 0; i < nr_fixed_counters; i++) { - cnt[n].count = 0; cnt[n].ctr = fixed_events[i].unit_sel; cnt[n].config = EVNTSEL_OS | EVNTSEL_USR; n++; @@ -283,9 +291,8 @@ static void check_counter_overflow(void) pmu_counter_t cnt = { .ctr = gp_counter_base, .config = EVNTSEL_OS | EVNTSEL_USR | gp_events[1].unit_sel /* instructions */, - .count = 0, }; - measure(&cnt, 1); + __measure(&cnt, 0); count = cnt.count; /* clear status before test */ @@ -311,7 +318,7 @@ static void check_counter_overflow(void) else cnt.config &= ~EVNTSEL_INT; idx = event_to_global_idx(&cnt); - measure(&cnt, 1); + __measure(&cnt, cnt.count); report(cnt.count == 1, "cntr-%d", i); status = rdmsr(MSR_CORE_PERF_GLOBAL_STATUS); report(status & (1ull << idx), "status-%d", i); @@ -329,7 +336,6 @@ static void check_gp_counter_cmask(void) pmu_counter_t cnt = { .ctr = gp_counter_base, .config = EVNTSEL_OS | EVNTSEL_USR | gp_events[1].unit_sel /* instructions */, - .count = 0, }; cnt.config |= (0x2 << EVNTSEL_CMASK_SHIFT); measure(&cnt, 1); @@ -415,7 +421,6 @@ static void check_running_counter_wrmsr(void) pmu_counter_t evt = { .ctr = gp_counter_base, .config = EVNTSEL_OS | EVNTSEL_USR | gp_events[1].unit_sel, - .count = 0, }; report_prefix_push("running counter wrmsr"); @@ -430,7 +435,6 @@ static void check_running_counter_wrmsr(void) wrmsr(MSR_CORE_PERF_GLOBAL_OVF_CTRL, rdmsr(MSR_CORE_PERF_GLOBAL_STATUS)); - evt.count = 0; start_event(&evt); count = -1; @@ -454,13 +458,11 @@ static void check_emulated_instr(void) .ctr = MSR_IA32_PERFCTR0, /* branch instructions */ .config = EVNTSEL_OS | EVNTSEL_USR | gp_events[5].unit_sel, - .count = 0, }; pmu_counter_t instr_cnt = { .ctr = MSR_IA32_PERFCTR0 + 1, /* instructions */ .config = EVNTSEL_OS | EVNTSEL_USR | gp_events[1].unit_sel, - .count = 0, }; report_prefix_push("emulated instruction"); @@ -589,7 +591,6 @@ static void set_ref_cycle_expectations(void) pmu_counter_t cnt = { .ctr = MSR_IA32_PERFCTR0, .config = EVNTSEL_OS | EVNTSEL_USR | gp_events[2].unit_sel, - .count = 0, }; uint64_t tsc_delta; uint64_t t0, t1, t2, t3; -- 2.37.2