rdpmc.c

#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/mman.h>
#include <linux/types.h>
#include "perf.h"
#include "debug.h"
#include "tests/tests.h"
#include "cloexec.h"
#include "arch-tests.h"

static u64 rdpmc(unsigned int counter)
{
	unsigned int low, high;

	asm volatile("rdpmc" : "=a" (low), "=d" (high) : "c" (counter));

	return low | ((u64)high) << 32;
}

static u64 rdtsc(void)
{
	unsigned int low, high;

	asm volatile("rdtsc" : "=a" (low), "=d" (high));

	return low | ((u64)high) << 32;
}

static u64 mmap_read_self(void *addr)
{
	struct perf_event_mmap_page *pc = addr;
	u32 seq, idx, time_mult = 0, time_shift = 0;
	u64 count, cyc = 0, time_offset = 0, enabled, running, delta;

	do {
		seq = pc->lock;
		barrier();

		enabled = pc->time_enabled;
		running = pc->time_running;

		if (enabled != running) {
			cyc = rdtsc();
			time_mult = pc->time_mult;
			time_shift = pc->time_shift;
			time_offset = pc->time_offset;
		}

		idx = pc->index;
		count = pc->offset;
		if (idx)
			count += rdpmc(idx - 1);

		barrier();
	} while (pc->lock != seq);

	if (enabled != running) {
		u64 quot, rem;

		quot = (cyc >> time_shift);
		rem = cyc & (((u64)1 << time_shift) - 1);
		delta = time_offset + quot * time_mult +
			((rem * time_mult) >> time_shift);

		enabled += delta;
		if (idx)
			running += delta;

		quot = count / running;