From: Rob Herring <r...@kernel.org>
commit 47d01e7b9999b9591077a59a1ecec11c6ce570de upstream
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 userspace access, an event must be mmapped first
with perf_evsel__mmap(). Then subsequent calls to perf_evsel__read()
will use the fast path (assuming the arch supports it).
Committer notes:
Added a '__maybe_unused' attribute to the read_perf_counter() argument
to fix the build on arches other than x86_64 and arm.
Committer testing:
Building and running the libperf tests in verbose mode (V=1) now shows
those "loop = N, count = N" extra lines, testing user space counter
access.
# make V=1 -C tools/lib/perf tests
make: Entering directory '/home/acme/git/perf/tools/lib/perf'
make -f /home/acme/git/perf/tools/build/Makefile.build dir=. obj=libperf
make -C /home/acme/git/perf/tools/lib/api/ O= libapi.a
make -f /home/acme/git/perf/tools/build/Makefile.build dir=./fd obj=libapi
make -f /home/acme/git/perf/tools/build/Makefile.build dir=./fs obj=libapi
make -C tests
gcc -I/home/acme/git/perf/tools/lib/perf/include
-I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall -o
test-cpumap-a test-cpumap.c ../libperf.a
/home/acme/git/perf/tools/lib/api/libapi.a
gcc -I/home/acme/git/perf/tools/lib/perf/include
-I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall -o
test-threadmap-a test-threadmap.c ../libperf.a
/home/acme/git/perf/tools/lib/api/libapi.a
gcc -I/home/acme/git/perf/tools/lib/perf/include
-I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall -o
test-evlist-a test-evlist.c ../libperf.a
/home/acme/git/perf/tools/lib/api/libapi.a
gcc -I/home/acme/git/perf/tools/lib/perf/include
-I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall -o
test-evsel-a test-evsel.c ../libperf.a
/home/acme/git/perf/tools/lib/api/libapi.a
gcc -I/home/acme/git/perf/tools/lib/perf/include
-I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall
-L.. -o test-cpumap-so test-cpumap.c /home/acme/git/perf/tools/lib/api/libapi.a
-lperf
gcc -I/home/acme/git/perf/tools/lib/perf/include
-I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall
-L.. -o test-threadmap-so test-threadmap.c
/home/acme/git/perf/tools/lib/api/libapi.a -lperf
gcc -I/home/acme/git/perf/tools/lib/perf/include
-I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall
-L.. -o test-evlist-so test-evlist.c /home/acme/git/perf/tools/lib/api/libapi.a
-lperf
gcc -I/home/acme/git/perf/tools/lib/perf/include
-I/home/acme/git/perf/tools/include -I/home/acme/git/perf/tools/lib -g -Wall
-L.. -o test-evsel-so test-evsel.c /home/acme/git/perf/tools/lib/api/libapi.a
-lperf
make -C tests run
running static:
- running test-cpumap.c...OK
- running test-threadmap.c...OK
- running test-evlist.c...OK
- running test-evsel.c...
loop = 65536, count = 333926
loop = 131072, count = 655781
loop = 262144, count = 1311141
loop = 524288, count = 2630126
loop = 1048576, count = 5256955
loop = 65536, count = 524594
loop = 131072, count = 1058916
loop = 262144, count = 2097458
loop = 524288, count = 4205429
loop = 1048576, count = 8406606
OK
running dynamic:
- running test-cpumap.c...OK
- running test-threadmap.c...OK
- running test-evlist.c...OK
- running test-evsel.c...
loop = 65536, count = 328102
loop = 131072, count = 655782
loop = 262144, count = 1317494
loop = 524288, count = 2627851
loop = 1048576, count = 5255187
loop = 65536, count = 524601
loop = 131072, count = 1048923
loop = 262144, count = 2107917
loop = 524288, count = 4194606
loop = 1048576, count = 8409322
OK
make: Leaving directory '/home/acme/git/perf/tools/lib/perf'
#
Signed-off-by: Rob Herring <r...@kernel.org>
Acked-by: Jiri Olsa <jo...@redhat.com>
Acked-by: Namhyung Kim <namhy...@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <a...@redhat.com>
Cc: Catalin Marinas <catalin.mari...@arm.com>
Cc: Itaru Kitayama <itaru.kitay...@gmail.com>
Cc: Mark Rutland <mark.rutl...@arm.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Will Deacon <w...@kernel.org>
Link: http://lore.kernel.org/lkml/20210414155412.3697605-4-r...@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.com>
Signed-off-by: Adrian Zaharia <adrian.zaha...@windriver.com>
---
tools/lib/perf/evsel.c | 4 ++
tools/lib/perf/include/internal/mmap.h | 3 +
tools/lib/perf/mmap.c | 88 ++++++++++++++++++++++++++
tools/lib/perf/tests/test-evsel.c | 66 +++++++++++++++++++
4 files changed, 161 insertions(+)
diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
index cd203998e875..bd8c2f19ef74 100644
--- a/tools/lib/perf/evsel.c
+++ b/tools/lib/perf/evsel.c
@@ -267,6 +267,10 @@ int perf_evsel__read(struct perf_evsel *evsel, int cpu,
int thread,
if (FD(evsel, cpu, thread) < 0)
return -EINVAL;
+ if (MMAP(evsel, cpu, thread) &&
+ !perf_mmap__read_self(MMAP(evsel, cpu, thread), count))
+ return 0;
+
if (readn(FD(evsel, cpu, thread), count->values, size) <= 0)
return -errno;
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/mmap.c b/tools/lib/perf/mmap.c
index 79d5ed6c38cc..c89dfa5f67b3 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 +275,89 @@ 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 __maybe_unused) { 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;
+
+ if (!pc || !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) {
+ s64 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 2de98768d844..0b7ce456f1ba 100644
--- a/tools/lib/perf/tests/test-evsel.c
+++ b/tools/lib/perf/tests/test-evsel.c
@@ -120,6 +120,70 @@ 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);
+
+ err = perf_evsel__mmap(evsel, 0);
+ __T("failed to mmap evsel", err == 0);
+
+ pc = perf_evsel__mmap_base(evsel, 0, 0);
+
+#if defined(__i386__) || defined(__x86_64__)
+ __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);
+
+ for (i = 0; i < 5; i++) {
+ volatile int count = 0x10000 << i;
+ __u64 start, end, last = 0;
+
+ __T_VERBOSE("\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;
+ __T_VERBOSE("count = %llu\n", end - start);
+ }
+
+ perf_evsel__munmap(evsel);
+ 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 +193,8 @@ 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 tests_failed == 0 ? 0 : -1;
--
2.36.1
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