// SPDX-License-Identifier: GPL-2.0-only
/*
 * Benchmarking code execution time inside the kernel
 *
 * Copyright (C) 2014, Red Hat, Inc., Jesper Dangaard Brouer
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/time.h>

#include <linux/perf_event.h> /* perf_event_create_kernel_counter() */

/* For concurrency testing */
#include <linux/completion.h>
#include <linux/sched.h>
#include <linux/workqueue.h>
#include <linux/kthread.h>

#include "time_bench.h"

static int verbose = 1;

/** TSC (Time-Stamp Counter) based **
 * See: linux/time_bench.h
 *  tsc_start_clock() and tsc_stop_clock()
 */

/** Wall-clock based **
 */

/** PMU (Performance Monitor Unit) based **
 */
#define PERF_FORMAT                                                            \
	(PERF_FORMAT_GROUP | PERF_FORMAT_ID | PERF_FORMAT_TOTAL_TIME_ENABLED | \
	 PERF_FORMAT_TOTAL_TIME_RUNNING)

struct raw_perf_event {
	uint64_t config; /* event */
	uint64_t config1; /* umask */
	struct perf_event *save;
	char *desc;
};

/* if HT is enable a maximum of 4 events (5 if one is instructions
 * retired can be specified, if HT is disabled a maximum of 8 (9 if
 * one is instructions retired) can be specified.
 *
 * From Table 19-1. Architectural Performance Events
 * Architectures Software Developer’s Manual Volume 3: System Programming
 * Guide
 */
struct raw_perf_event perf_events[] = {
	{ 0x3c, 0x00, NULL, "Unhalted CPU Cycles" },
	{ 0xc0, 0x00, NULL, "Instruction Retired" }
};

#define NUM_EVTS (ARRAY_SIZE(perf_events))

/* WARNING: PMU config is currently broken!
 */
bool time_bench_PMU_config(bool enable)
{
	int i;
	struct perf_event_attr perf_conf;
	struct perf_event *perf_event;
	int cpu;

	preempt_disable();
	cpu = smp_processor_id();
	pr_info("DEBUG: cpu:%d\n", cpu);
	preempt_enable();

	memset(&perf_conf, 0, sizeof(struct perf_event_attr));
	perf_conf.type           = PERF_TYPE_RAW;
	perf_conf.size           = sizeof(struct perf_event_attr);
	perf_conf.read_format    = PERF_FORMAT;
	perf_conf.pinned         = 1;
	perf_conf.exclude_user   = 1; /* No userspace events */
	perf_conf.exclude_kernel = 0; /* Only kernel events */

	for (i = 0; i < NUM_EVTS; i++) {
		perf_conf.disabled = enable;
		//perf_conf.disabled = (i == 0) ? 1 : 0;
		perf_conf.config   = perf_events[i].config;
		perf_conf.config1  = perf_events[i].config1;
		if (verbose)
			pr_info("%s() enable PMU counter: %s\n",
				__func__, perf_events[i].desc);
		perf_event = perf_event_create_kernel_counter(&perf_conf, cpu,
							      NULL /* task */,
							      NULL /* overflow_handler*/,
							      NULL /* context */);
		if (perf_event) {
			perf_events[i].save = perf_event;
			pr_info("%s():DEBUG perf_event success\n", __func__);

			perf_event_enable(perf_event);
		} else {
			pr_info("%s():DEBUG perf_event is NULL\n", __func__);
		}
	}

	return true;
}

/** Generic functions **
 */

/* Calculate stats, store results in record */
bool time_bench_calc_stats(struct time_bench_record *rec)
{
#define NANOSEC_PER_SEC 1000000000 /* 10^9 */
	uint64_t ns_per_call_tmp_rem = 0;
	uint32_t ns_per_call_remainder = 0;
	uint64_t pmc_ipc_tmp_rem = 0;
	uint32_t pmc_ipc_remainder = 0;
	uint32_t pmc_ipc_div = 0;
	uint32_t invoked_cnt_precision = 0;
	uint32_t invoked_cnt = 0; /* 32-bit due to div_u64_rem() */

	if (rec->flags & TIME_BENCH_LOOP) {
		if (rec->invoked_cnt < 1000) {
			pr_err("ERR: need more(>1000) loops(%llu) for timing\n",
			       rec->invoked_cnt);
			return false;
		}
		if (rec->invoked_cnt > ((1ULL << 32) - 1)) {
			/* div_u64_rem() can only support div with 32bit*/
			pr_err("ERR: Invoke cnt(%llu) too big overflow 32bit\n",
			       rec->invoked_cnt);
			return false;
		}
		invoked_cnt = (uint32_t)rec->invoked_cnt;
	}

	/* TSC (Time-Stamp Counter) records */
	if (rec->flags & TIME_BENCH_TSC) {
		rec->tsc_interval = rec->tsc_stop - rec->tsc_start;
		if (rec->tsc_interval == 0) {
			pr_err("ABORT: timing took ZERO TSC time\n");
			return false;
		}
		/* Calculate stats */
		if (rec->flags & TIME_BENCH_LOOP)
			rec->tsc_cycles = rec->tsc_interval / invoked_cnt;
		else
			rec->tsc_cycles = rec->tsc_interval;
	}

	/* Wall-clock time calc */
	if (rec->flags & TIME_BENCH_WALLCLOCK) {
		rec->time_start = rec->ts_start.tv_nsec +
				  (NANOSEC_PER_SEC * rec->ts_start.tv_sec);
		rec->time_stop = rec->ts_stop.tv_nsec +
				 (NANOSEC_PER_SEC * rec->ts_stop.tv_sec);
		rec->time_interval = rec->time_stop - rec->time_start;
		if (rec->time_interval == 0) {
			pr_err("ABORT: timing took ZERO wallclock time\n");
			return false;
		}
		/* Calculate stats */
		/*** Division in kernel it tricky ***/
		/* Orig: time_sec = (time_interval / NANOSEC_PER_SEC); */
		/* remainder only correct because NANOSEC_PER_SEC is 10^9 */
		rec->time_sec = div_u64_rem(rec->time_interval, NANOSEC_PER_SEC,
					    &rec->time_sec_remainder);
		//TODO: use existing struct timespec records instead of div?

		if (rec->flags & TIME_BENCH_LOOP) {
			/*** Division in kernel it tricky ***/
			/* Orig: ns = ((double)time_interval / invoked_cnt); */
			/* First get quotient */
			rec->ns_per_call_quotient =
				div_u64_rem(rec->time_interval, invoked_cnt,
					    &ns_per_call_remainder);
			/* Now get decimals .xxx precision (incorrect roundup)*/
			ns_per_call_tmp_rem = ns_per_call_remainder;
			invoked_cnt_precision = invoked_cnt / 1000;
			if (invoked_cnt_precision > 0) {
				rec->ns_per_call_decimal =
					div_u64_rem(ns_per_call_tmp_rem,
						    invoked_cnt_precision,
						    &ns_per_call_remainder);
			}
		}
	}

	/* Performance Monitor Unit (PMU) counters */
	if (rec->flags & TIME_BENCH_PMU) {
		//FIXME: Overflow handling???
		rec->pmc_inst = rec->pmc_inst_stop - rec->pmc_inst_start;
		rec->pmc_clk = rec->pmc_clk_stop - rec->pmc_clk_start;

		/* Calc Instruction Per Cycle (IPC) */
		/* First get quotient */
		rec->pmc_ipc_quotient = div_u64_rem(rec->pmc_inst, rec->pmc_clk,
						    &pmc_ipc_remainder);
		/* Now get decimals .xxx precision (incorrect roundup)*/
		pmc_ipc_tmp_rem = pmc_ipc_remainder;
		pmc_ipc_div = rec->pmc_clk / 1000;
		if (pmc_ipc_div > 0) {
			rec->pmc_ipc_decimal = div_u64_rem(pmc_ipc_tmp_rem,
							   pmc_ipc_div,
							   &pmc_ipc_remainder);
		}
	}

	return true;
}

/* Generic function for invoking a loop function and calculating
 * execution time stats.  The function being called/timed is assumed
 * to perform a tight loop, and update the timing record struct.
 */
bool time_bench_loop(uint32_t loops, int step, char *txt, void *data,
		     int (*func)(struct time_bench_record *record, void *data))
{
	struct time_bench_record rec;

	/* Setup record */
	memset(&rec, 0, sizeof(rec)); /* zero func might not update all */
	rec.version_abi = 1;
	rec.loops       = loops;
	rec.step        = step;
	rec.flags       = (TIME_BENCH_LOOP | TIME_BENCH_TSC | TIME_BENCH_WALLCLOCK);

	/*** Loop function being timed ***/
	if (!func(&rec, data)) {
		pr_err("ABORT: function being timed failed\n");
		return false;
	}

	if (rec.invoked_cnt < loops)
		pr_warn("WARNING: Invoke count(%llu) smaller than loops(%d)\n",
			rec.invoked_cnt, loops);

	/* Calculate stats */
	time_bench_calc_stats(&rec);

	pr_info("Type:%s Per elem: %llu cycles(tsc) %llu.%03llu ns (step:%d) - (measurement period time:%llu.%09u sec time_interval:%llu) - (invoke count:%llu tsc_interval:%llu)\n",
		txt, rec.tsc_cycles, rec.ns_per_call_quotient,
		rec.ns_per_call_decimal, rec.step, rec.time_sec,
		rec.time_sec_remainder, rec.time_interval, rec.invoked_cnt,
		rec.tsc_interval);
	if (rec.flags & TIME_BENCH_PMU)
		pr_info("Type:%s PMU inst/clock%llu/%llu = %llu.%03llu IPC (inst per cycle)\n",
			txt, rec.pmc_inst, rec.pmc_clk, rec.pmc_ipc_quotient,
			rec.pmc_ipc_decimal);
	return true;
}

/* Function getting invoked by kthread */
static int invoke_test_on_cpu_func(void *private)
{
	struct time_bench_cpu *cpu = private;
	struct time_bench_sync *sync = cpu->sync;
	cpumask_t newmask = CPU_MASK_NONE;
	void *data = cpu->data;

	/* Restrict CPU */
	cpumask_set_cpu(cpu->rec.cpu, &newmask);
	set_cpus_allowed_ptr(current, &newmask);

	/* Synchronize start of concurrency test */
	atomic_inc(&sync->nr_tests_running);
	wait_for_completion(&sync->start_event);

	/* Start benchmark function */
	if (!cpu->bench_func(&cpu->rec, data)) {
		pr_err("ERROR: function being timed failed on CPU:%d(%d)\n",
		       cpu->rec.cpu, smp_processor_id());
	} else {
		if (verbose)
			pr_info("SUCCESS: ran on CPU:%d(%d)\n", cpu->rec.cpu,
				smp_processor_id());
	}
	cpu->did_bench_run = true;

	/* End test */
	atomic_dec(&sync->nr_tests_running);
	/*  Wait for kthread_stop() telling us to stop */
	while (!kthread_should_stop()) {
		set_current_state(TASK_INTERRUPTIBLE);
		schedule();
	}
	__set_current_state(TASK_RUNNING);
	return 0;
}

void time_bench_print_stats_cpumask(const char *desc,
				    struct time_bench_cpu *cpu_tasks,
				    const struct cpumask *mask)
{
	uint64_t average = 0;
	int cpu;
	int step = 0;
	struct sum {
		uint64_t tsc_cycles;
		int records;
	} sum = { 0 };

	/* Get stats */
	for_each_cpu(cpu, mask) {
		struct time_bench_cpu *c = &cpu_tasks[cpu];
		struct time_bench_record *rec = &c->rec;

		/* Calculate stats */
		time_bench_calc_stats(rec);

		pr_info("Type:%s CPU(%d) %llu cycles(tsc) %llu.%03llu ns (step:%d) - (measurement period time:%llu.%09u sec time_interval:%llu) - (invoke count:%llu tsc_interval:%llu)\n",
			desc, cpu, rec->tsc_cycles, rec->ns_per_call_quotient,
			rec->ns_per_call_decimal, rec->step, rec->time_sec,
			rec->time_sec_remainder, rec->time_interval,
			rec->invoked_cnt, rec->tsc_interval);

		/* Collect average */
		sum.records++;
		sum.tsc_cycles += rec->tsc_cycles;
		step = rec->step;
	}

	if (sum.records) /* avoid div-by-zero */
		average = sum.tsc_cycles / sum.records;
	pr_info("Sum Type:%s Average: %llu cycles(tsc) CPUs:%d step:%d\n", desc,
		average, sum.records, step);
}

void time_bench_run_concurrent(uint32_t loops, int step, void *data,
			       const struct cpumask *mask, /* Support masking outsome CPUs*/
			       struct time_bench_sync *sync,
			       struct time_bench_cpu *cpu_tasks,
			       int (*func)(struct time_bench_record *record, void *data))
{
	int cpu, running = 0;

	if (verbose) // DEBUG
		pr_warn("%s() Started on CPU:%d\n", __func__,
			smp_processor_id());

	/* Reset sync conditions */
	atomic_set(&sync->nr_tests_running, 0);
	init_completion(&sync->start_event);

	/* Spawn off jobs on all CPUs */
	for_each_cpu(cpu, mask) {
		struct time_bench_cpu *c = &cpu_tasks[cpu];

		running++;
		c->sync = sync; /* Send sync variable along */
		c->data = data; /* Send opaque along */

		/* Init benchmark record */
		memset(&c->rec, 0, sizeof(struct time_bench_record));
		c->rec.version_abi = 1;
		c->rec.loops       = loops;
		c->rec.step        = step;
		c->rec.flags       = (TIME_BENCH_LOOP | TIME_BENCH_TSC |
				      TIME_BENCH_WALLCLOCK);
		c->rec.cpu = cpu;
		c->bench_func = func;
		c->task = kthread_run(invoke_test_on_cpu_func, c,
				      "time_bench%d", cpu);
		if (IS_ERR(c->task)) {
			pr_err("%s(): Failed to start test func\n", __func__);
			return; /* Argh, what about cleanup?! */
		}
	}

	/* Wait until all processes are running */
	while (atomic_read(&sync->nr_tests_running) < running) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule_timeout(10);
	}
	/* Kick off all CPU concurrently on completion event */
	complete_all(&sync->start_event);

	/* Wait for CPUs to finish */
	while (atomic_read(&sync->nr_tests_running)) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule_timeout(10);
	}

	/* Stop the kthreads */
	for_each_cpu(cpu, mask) {
		struct time_bench_cpu *c = &cpu_tasks[cpu];

		kthread_stop(c->task);
	}

	if (verbose) // DEBUG - happens often, finish on another CPU
		pr_warn("%s() Finished on CPU:%d\n", __func__,
			smp_processor_id());
}