x86 and arm64 can both support direct access of event counters in userspace. The access sequence is less than trivial and currently exists in perf test code (tools/perf/arch/x86/tests/rdpmc.c) with copies in projects such as PAPI and libpfm4.
In order to support usersapce access, an event must be mmapped. While there's already mmap support for evlist, the usecase is a bit different than the self monitoring with userspace access. So let's add a new perf_evsel__mmap() function to mmap an evsel. This allows implementing userspace access as a fastpath for perf_evsel__read(). The mmapped address is returned by perf_evsel__mmap() primarily for users/tests to check if userspace access is enabled. Signed-off-by: Rob Herring <[email protected]> --- tools/lib/perf/Documentation/libperf.txt | 1 + tools/lib/perf/evsel.c | 33 +++++++++ tools/lib/perf/include/internal/evsel.h | 2 + tools/lib/perf/include/internal/mmap.h | 3 + tools/lib/perf/include/perf/evsel.h | 1 + tools/lib/perf/libperf.map | 1 + tools/lib/perf/mmap.c | 90 ++++++++++++++++++++++++ tools/lib/perf/tests/test-evsel.c | 64 +++++++++++++++++ 8 files changed, 195 insertions(+) diff --git a/tools/lib/perf/Documentation/libperf.txt b/tools/lib/perf/Documentation/libperf.txt index 0c74c30ed23a..ca7478acc97c 100644 --- a/tools/lib/perf/Documentation/libperf.txt +++ b/tools/lib/perf/Documentation/libperf.txt @@ -136,6 +136,7 @@ SYNOPSIS struct perf_thread_map *threads); void perf_evsel__close(struct perf_evsel *evsel); void perf_evsel__close_cpu(struct perf_evsel *evsel, int cpu); + void *perf_evsel__mmap(struct perf_evsel *evsel); int perf_evsel__read(struct perf_evsel *evsel, int cpu, int thread, struct perf_counts_values *count); int perf_evsel__enable(struct perf_evsel *evsel); diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c index 4dc06289f4c7..b0c94ef4d9b6 100644 --- a/tools/lib/perf/evsel.c +++ b/tools/lib/perf/evsel.c @@ -11,10 +11,12 @@ #include <stdlib.h> #include <internal/xyarray.h> #include <internal/cpumap.h> +#include <internal/mmap.h> #include <internal/threadmap.h> #include <internal/lib.h> #include <linux/string.h> #include <sys/ioctl.h> +#include <sys/mman.h> void perf_evsel__init(struct perf_evsel *evsel, struct perf_event_attr *attr) { @@ -156,6 +158,34 @@ void perf_evsel__close_cpu(struct perf_evsel *evsel, int cpu) perf_evsel__close_fd_cpu(evsel, cpu); } +void *perf_evsel__mmap(struct perf_evsel *evsel) +{ + int ret; + struct perf_mmap *map; + struct perf_mmap_param mp = { + .mask = -1, + .prot = PROT_READ | PROT_WRITE, + }; + + if (FD(evsel, 0, 0) < 0) + return NULL; + + map = zalloc(sizeof(*map)); + if (!map) + return NULL; + + perf_mmap__init(map, NULL, false, NULL); + + ret = perf_mmap__mmap(map, &mp, FD(evsel, 0, 0), 0); + if (ret) { + free(map); + return NULL; + } + + evsel->mmap = map; + return map->base; +} + int perf_evsel__read_size(struct perf_evsel *evsel) { u64 read_format = evsel->attr.read_format; @@ -191,6 +221,9 @@ int perf_evsel__read(struct perf_evsel *evsel, int cpu, int thread, if (FD(evsel, cpu, thread) < 0) return -EINVAL; + if (evsel->mmap && !perf_mmap__read_self(evsel->mmap, count)) + return 0; + if (readn(FD(evsel, cpu, thread), count->values, size) <= 0) return -errno; diff --git a/tools/lib/perf/include/internal/evsel.h b/tools/lib/perf/include/internal/evsel.h index 1ffd083b235e..a7985dbb68ff 100644 --- a/tools/lib/perf/include/internal/evsel.h +++ b/tools/lib/perf/include/internal/evsel.h @@ -9,6 +9,7 @@ struct perf_cpu_map; struct perf_thread_map; +struct perf_mmap; struct xyarray; /* @@ -40,6 +41,7 @@ struct perf_evsel { struct perf_cpu_map *cpus; struct perf_cpu_map *own_cpus; struct perf_thread_map *threads; + struct perf_mmap *mmap; struct xyarray *fd; struct xyarray *sample_id; u64 *id; diff --git a/tools/lib/perf/include/internal/mmap.h b/tools/lib/perf/include/internal/mmap.h index be7556e0a2b2..5e3422f40ed5 100644 --- a/tools/lib/perf/include/internal/mmap.h +++ b/tools/lib/perf/include/internal/mmap.h @@ -11,6 +11,7 @@ #define PERF_SAMPLE_MAX_SIZE (1 << 16) struct perf_mmap; +struct perf_counts_values; typedef void (*libperf_unmap_cb_t)(struct perf_mmap *map); @@ -52,4 +53,6 @@ void perf_mmap__put(struct perf_mmap *map); u64 perf_mmap__read_head(struct perf_mmap *map); +int perf_mmap__read_self(struct perf_mmap *map, struct perf_counts_values *count); + #endif /* __LIBPERF_INTERNAL_MMAP_H */ diff --git a/tools/lib/perf/include/perf/evsel.h b/tools/lib/perf/include/perf/evsel.h index c82ec39a4ad0..6d0da962870c 100644 --- a/tools/lib/perf/include/perf/evsel.h +++ b/tools/lib/perf/include/perf/evsel.h @@ -27,6 +27,7 @@ LIBPERF_API int perf_evsel__open(struct perf_evsel *evsel, struct perf_cpu_map * struct perf_thread_map *threads); LIBPERF_API void perf_evsel__close(struct perf_evsel *evsel); LIBPERF_API void perf_evsel__close_cpu(struct perf_evsel *evsel, int cpu); +LIBPERF_API void *perf_evsel__mmap(struct perf_evsel *evsel); LIBPERF_API int perf_evsel__read(struct perf_evsel *evsel, int cpu, int thread, struct perf_counts_values *count); LIBPERF_API int perf_evsel__enable(struct perf_evsel *evsel); diff --git a/tools/lib/perf/libperf.map b/tools/lib/perf/libperf.map index 7be1af8a546c..733a0647be8b 100644 --- a/tools/lib/perf/libperf.map +++ b/tools/lib/perf/libperf.map @@ -23,6 +23,7 @@ LIBPERF_0.0.1 { perf_evsel__disable; perf_evsel__open; perf_evsel__close; + perf_evsel__mmap; perf_evsel__read; perf_evsel__cpus; perf_evsel__threads; diff --git a/tools/lib/perf/mmap.c b/tools/lib/perf/mmap.c index 79d5ed6c38cc..cb07969cfdbf 100644 --- a/tools/lib/perf/mmap.c +++ b/tools/lib/perf/mmap.c @@ -8,9 +8,11 @@ #include <linux/perf_event.h> #include <perf/mmap.h> #include <perf/event.h> +#include <perf/evsel.h> #include <internal/mmap.h> #include <internal/lib.h> #include <linux/kernel.h> +#include <linux/math64.h> #include "internal.h" void perf_mmap__init(struct perf_mmap *map, struct perf_mmap *prev, @@ -273,3 +275,91 @@ union perf_event *perf_mmap__read_event(struct perf_mmap *map) return event; } + +#if defined(__i386__) || defined(__x86_64__) +static u64 read_perf_counter(unsigned int counter) +{ + unsigned int low, high; + + asm volatile("rdpmc" : "=a" (low), "=d" (high) : "c" (counter)); + + return low | ((u64)high) << 32; +} + +static u64 read_timestamp(void) +{ + unsigned int low, high; + + asm volatile("rdtsc" : "=a" (low), "=d" (high)); + + return low | ((u64)high) << 32; +} +#else +static u64 read_perf_counter(unsigned int counter) { return 0; } +static u64 read_timestamp(void) { return 0; } +#endif + +int perf_mmap__read_self(struct perf_mmap *map, struct perf_counts_values *count) +{ + struct perf_event_mmap_page *pc = map->base; + u32 seq, idx, time_mult = 0, time_shift = 0; + u64 cnt, cyc = 0, time_offset = 0, time_cycles = 0, time_mask = ~0ULL; + + BUG_ON(!pc); + + if (!pc->cap_user_rdpmc) + return -1; + + do { + seq = READ_ONCE(pc->lock); + barrier(); + + count->ena = READ_ONCE(pc->time_enabled); + count->run = READ_ONCE(pc->time_running); + + if (pc->cap_user_time && count->ena != count->run) { + cyc = read_timestamp(); + time_mult = READ_ONCE(pc->time_mult); + time_shift = READ_ONCE(pc->time_shift); + time_offset = READ_ONCE(pc->time_offset); + + if (pc->cap_user_time_short) { + time_cycles = READ_ONCE(pc->time_cycles); + time_mask = READ_ONCE(pc->time_mask); + } + } + + idx = READ_ONCE(pc->index); + cnt = READ_ONCE(pc->offset); + if (pc->cap_user_rdpmc && idx) { + u64 evcnt = read_perf_counter(idx - 1); + u16 width = READ_ONCE(pc->pmc_width); + + evcnt <<= 64 - width; + evcnt >>= 64 - width; + cnt += evcnt; + } else + return -1; + + barrier(); + } while (READ_ONCE(pc->lock) != seq); + + if (count->ena != count->run) { + u64 delta; + + /* Adjust for cap_usr_time_short, a nop if not */ + cyc = time_cycles + ((cyc - time_cycles) & time_mask); + + delta = time_offset + mul_u64_u32_shr(cyc, time_mult, time_shift); + + count->ena += delta; + if (idx) + count->run += delta; + + cnt = mul_u64_u64_div64(cnt, count->ena, count->run); + } + + count->val = cnt; + + return 0; +} diff --git a/tools/lib/perf/tests/test-evsel.c b/tools/lib/perf/tests/test-evsel.c index 135722ac965b..fd637d23216b 100644 --- a/tools/lib/perf/tests/test-evsel.c +++ b/tools/lib/perf/tests/test-evsel.c @@ -120,6 +120,68 @@ static int test_stat_thread_enable(void) return 0; } +static int test_stat_user_read(int event) +{ + struct perf_counts_values counts = { .val = 0 }; + struct perf_thread_map *threads; + struct perf_evsel *evsel; + struct perf_event_mmap_page *pc; + struct perf_event_attr attr = { + .type = PERF_TYPE_HARDWARE, + .config = event, + }; + int err, i; + + threads = perf_thread_map__new_dummy(); + __T("failed to create threads", threads); + + perf_thread_map__set_pid(threads, 0, 0); + + evsel = perf_evsel__new(&attr); + __T("failed to create evsel", evsel); + + err = perf_evsel__open(evsel, NULL, threads); + __T("failed to open evsel", err == 0); + + pc = perf_evsel__mmap(evsel); + __T("failed to mmap evsel", pc); + +#if defined(__i386__) || defined(__x86_64__) || defined(__aarch64__) + __T("userspace counter access not supported", pc->cap_user_rdpmc); + __T("userspace counter access not enabled", pc->index); + __T("userspace counter width not set", pc->pmc_width >= 32); +#endif + + perf_evsel__read(evsel, 0, 0, &counts); + __T("failed to read value for evsel", counts.val != 0); + + fputs("\n", stderr); + for (i = 0; i < 5; i++) { + volatile int count = 0x10000 << i; + __u64 start, end, last = 0; + + fprintf(stderr, "\tloop = %u, ", count); + + perf_evsel__read(evsel, 0, 0, &counts); + start = counts.val; + + while (count--) ; + + perf_evsel__read(evsel, 0, 0, &counts); + end = counts.val; + + __T("invalid counter data", (end - start) > last); + last = end - start; + fprintf(stderr, "count = %llu\n", end - start); + } + + perf_evsel__close(evsel); + perf_evsel__delete(evsel); + + perf_thread_map__put(threads); + return 0; +} + int main(int argc, char **argv) { __T_START; @@ -129,6 +191,8 @@ int main(int argc, char **argv) test_stat_cpu(); test_stat_thread(); test_stat_thread_enable(); + test_stat_user_read(PERF_COUNT_HW_INSTRUCTIONS); + test_stat_user_read(PERF_COUNT_HW_CPU_CYCLES); __T_END; return 0; -- 2.25.1
