diff options
| -rw-r--r-- | arch/x86/kernel/cpu/perf_event.c | 10 | ||||
| -rw-r--r-- | include/linux/perf_event.h | 83 | ||||
| -rw-r--r-- | kernel/events/core.c | 4 |
3 files changed, 84 insertions, 13 deletions
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index 453ac9497574..4ef8104958ee 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -1622,6 +1622,9 @@ static int x86_pmu_event_idx(struct perf_event *event) { int idx = event->hw.idx; + if (!x86_pmu.attr_rdpmc) + return 0; + if (x86_pmu.num_counters_fixed && idx >= X86_PMC_IDX_FIXED) { idx -= X86_PMC_IDX_FIXED; idx |= 1 << 30; @@ -1706,14 +1709,19 @@ static struct pmu pmu = { .flush_branch_stack = x86_pmu_flush_branch_stack, }; -void perf_update_user_clock(struct perf_event_mmap_page *userpg, u64 now) +void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now) { + userpg->cap_usr_time = 0; + userpg->cap_usr_rdpmc = x86_pmu.attr_rdpmc; + userpg->pmc_width = x86_pmu.cntval_bits; + if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) return; if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC)) return; + userpg->cap_usr_time = 1; userpg->time_mult = this_cpu_read(cyc2ns); userpg->time_shift = CYC2NS_SCALE_FACTOR; userpg->time_offset = this_cpu_read(cyc2ns_offset) - now; diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 57ae485e80fc..ca9ed4e6a286 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -299,18 +299,31 @@ struct perf_event_mmap_page { /* * Bits needed to read the hw events in user-space. * - * u32 seq; - * s64 count; + * u32 seq, time_mult, time_shift, idx, width; + * u64 count, enabled, running; + * u64 cyc, time_offset; + * s64 pmc = 0; * * do { * seq = pc->lock; - * * barrier() - * if (pc->index) { - * count = pmc_read(pc->index - 1); - * count += pc->offset; - * } else - * goto regular_read; + * + * enabled = pc->time_enabled; + * running = pc->time_running; + * + * if (pc->cap_usr_time && enabled != running) { + * cyc = rdtsc(); + * time_offset = pc->time_offset; + * time_mult = pc->time_mult; + * time_shift = pc->time_shift; + * } + * + * idx = pc->index; + * count = pc->offset; + * if (pc->cap_usr_rdpmc && idx) { + * width = pc->pmc_width; + * pmc = rdpmc(idx - 1); + * } * * barrier(); * } while (pc->lock != seq); @@ -323,14 +336,57 @@ struct perf_event_mmap_page { __s64 offset; /* add to hardware event value */ __u64 time_enabled; /* time event active */ __u64 time_running; /* time event on cpu */ - __u32 time_mult, time_shift; + union { + __u64 capabilities; + __u64 cap_usr_time : 1, + cap_usr_rdpmc : 1, + cap_____res : 62; + }; + + /* + * If cap_usr_rdpmc this field provides the bit-width of the value + * read using the rdpmc() or equivalent instruction. This can be used + * to sign extend the result like: + * + * pmc <<= 64 - width; + * pmc >>= 64 - width; // signed shift right + * count += pmc; + */ + __u16 pmc_width; + + /* + * If cap_usr_time the below fields can be used to compute the time + * delta since time_enabled (in ns) using rdtsc or similar. + * + * u64 quot, rem; + * u64 delta; + * + * quot = (cyc >> time_shift); + * rem = cyc & ((1 << time_shift) - 1); + * delta = time_offset + quot * time_mult + + * ((rem * time_mult) >> time_shift); + * + * Where time_offset,time_mult,time_shift and cyc are read in the + * seqcount loop described above. This delta can then be added to + * enabled and possible running (if idx), improving the scaling: + * + * enabled += delta; + * if (idx) + * running += delta; + * + * quot = count / running; + * rem = count % running; + * count = quot * enabled + (rem * enabled) / running; + */ + __u16 time_shift; + __u32 time_mult; __u64 time_offset; /* * Hole for extension of the self monitor capabilities */ - __u64 __reserved[121]; /* align to 1k */ + __u64 __reserved[120]; /* align to 1k */ /* * Control data for the mmap() data buffer. @@ -347,6 +403,13 @@ struct perf_event_mmap_page { __u64 data_tail; /* user-space written tail */ }; +/* + * Build time assertion that we keep the data_head at the intended location. + * IOW, validation we got the __reserved[] size right. + */ +extern char __assert_mmap_data_head_offset + [1 - 2*!!(offsetof(struct perf_event_mmap_page, data_head) != 1024)]; + #define PERF_RECORD_MISC_CPUMODE_MASK (7 << 0) #define PERF_RECORD_MISC_CPUMODE_UNKNOWN (0 << 0) #define PERF_RECORD_MISC_KERNEL (1 << 0) diff --git a/kernel/events/core.c b/kernel/events/core.c index c61234b1a988..dc3b05272511 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3348,7 +3348,7 @@ static void calc_timer_values(struct perf_event *event, *running = ctx_time - event->tstamp_running; } -void __weak perf_update_user_clock(struct perf_event_mmap_page *userpg, u64 now) +void __weak arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now) { } @@ -3398,7 +3398,7 @@ void perf_event_update_userpage(struct perf_event *event) userpg->time_running = running + atomic64_read(&event->child_total_time_running); - perf_update_user_clock(userpg, now); + arch_perf_update_userpage(userpg, now); barrier(); ++userpg->lock; |