/*
 * Copyright (c) 2016 Facebook
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 */
#define _GNU_SOURCE
#include <linux/types.h>
#include <stdio.h>
#include <unistd.h>
#include <linux/bpf.h>
#include <errno.h>
#include <string.h>
#include <assert.h>
#include <sched.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <sys/resource.h>
#include <fcntl.h>
#include <stdlib.h>
#include <time.h>

#include "libbpf.h"
#include "bpf_util.h"

#define min(a, b) ((a) < (b) ? (a) : (b))
#ifndef offsetof
# define offsetof(TYPE, MEMBER) ((size_t)&((TYPE *)0)->MEMBER)
#endif
#define container_of(ptr, type, member) ({                      \
        const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
        (type *)( (char *)__mptr - offsetof(type,member) );})

static int nr_cpus;
static unsigned long long *dist_keys;
static unsigned int dist_key_counts;

struct list_head {
        struct list_head *next, *prev;
};

static inline void INIT_LIST_HEAD(struct list_head *list)
{
        list->next = list;
        list->prev = list;
}

static inline int list_empty(const struct list_head *head)
{
        return head->next == head;
}

static inline void __list_add(struct list_head *new,
                              struct list_head *prev,
                              struct list_head *next)
{
        next->prev = new;
        new->next = next;
        new->prev = prev;
        prev->next = new;
}

static inline void list_add(struct list_head *new, struct list_head *head)
{
        __list_add(new, head, head->next);
}

static inline void __list_del(struct list_head *prev, struct list_head *next)
{
        next->prev = prev;
        prev->next = next;
}

static inline void __list_del_entry(struct list_head *entry)
{
        __list_del(entry->prev, entry->next);
}

static inline void list_move(struct list_head *list, struct list_head *head)
{
        __list_del_entry(list);
        list_add(list, head);
}

#define list_entry(ptr, type, member) \
        container_of(ptr, type, member)

#define list_last_entry(ptr, type, member) \
        list_entry((ptr)->prev, type, member)

struct pfect_lru_node {
        struct list_head list;
        unsigned long long key;
};

struct pfect_lru {
        struct list_head list;
        struct pfect_lru_node *free_nodes;
        unsigned int cur_size;
        unsigned int lru_size;
        unsigned int nr_unique;
        unsigned int nr_misses;
        unsigned int total;
        int map_fd;
};

static void pfect_lru_init(struct pfect_lru *lru, unsigned int lru_size,
                           unsigned int nr_possible_elems)
{
        lru->map_fd = bpf_create_map(BPF_MAP_TYPE_HASH,
                                     sizeof(unsigned long long),
                                     sizeof(struct pfect_lru_node *),
                                     nr_possible_elems, 0);
        assert(lru->map_fd != -1);

        lru->free_nodes = malloc(lru_size * sizeof(struct pfect_lru_node));
        assert(lru->free_nodes);

        INIT_LIST_HEAD(&lru->list);
        lru->cur_size = 0;
        lru->lru_size = lru_size;
        lru->nr_unique = lru->nr_misses = lru->total = 0;
}

static void pfect_lru_destroy(struct pfect_lru *lru)
{
        close(lru->map_fd);
        free(lru->free_nodes);
}

static int pfect_lru_lookup_or_insert(struct pfect_lru *lru,
                                      unsigned long long key)
{
        struct pfect_lru_node *node = NULL;
        int seen = 0;

        lru->total++;
        if (!bpf_map_lookup_elem(lru->map_fd, &key, &node)) {
                if (node) {
                        list_move(&node->list, &lru->list);
                        return 1;
                }
                seen = 1;
        }

        if (lru->cur_size < lru->lru_size) {
                node =  &lru->free_nodes[lru->cur_size++];
                INIT_LIST_HEAD(&node->list);
        } else {
                struct pfect_lru_node *null_node = NULL;

                node = list_last_entry(&lru->list,
                                       struct pfect_lru_node,
                                       list);
                bpf_map_update_elem(lru->map_fd, &node->key, &null_node, BPF_EXIST);
        }

        node->key = key;
        list_move(&node->list, &lru->list);

        lru->nr_misses++;
        if (seen) {
                assert(!bpf_map_update_elem(lru->map_fd, &key, &node, BPF_EXIST));
        } else {
                lru->nr_unique++;
                assert(!bpf_map_update_elem(lru->map_fd, &key, &node, BPF_NOEXIST));
        }

        return seen;
}

static unsigned int read_keys(const char *dist_file,
                              unsigned long long **keys)
{
        struct stat fst;
        unsigned long long *retkeys;
        unsigned int counts = 0;
        int dist_fd;
        char *b, *l;
        int i;

        dist_fd = open(dist_file, 0);
        assert(dist_fd != -1);

        assert(fstat(dist_fd, &fst) == 0);
        b = malloc(fst.st_size);
        assert(b);

        assert(read(dist_fd, b, fst.st_size) == fst.st_size);
        close(dist_fd);
        for (i = 0; i < fst.st_size; i++) {
                if (b[i] == '\n')
                        counts++;
        }
        counts++; /* in case the last line has no \n */

        retkeys = malloc(counts * sizeof(unsigned long long));
        assert(retkeys);

        counts = 0;
        for (l = strtok(b, "\n"); l; l = strtok(NULL, "\n"))
                retkeys[counts++] = strtoull(l, NULL, 10);
        free(b);

        *keys = retkeys;

        return counts;
}

static int create_map(int map_type, int map_flags, unsigned int size)
{
        int map_fd;

        map_fd = bpf_create_map(map_type, sizeof(unsigned long long),
                                sizeof(unsigned long long), size, map_flags);

        if (map_fd == -1)
                perror("bpf_create_map");

        return map_fd;
}

static int sched_next_online(int pid, int next_to_try)
{
        cpu_set_t cpuset;

        if (next_to_try == nr_cpus)
                return -1;

        while (next_to_try < nr_cpus) {
                CPU_ZERO(&cpuset);
                CPU_SET(next_to_try++, &cpuset);
                if (!sched_setaffinity(pid, sizeof(cpuset), &cpuset))
                        break;
        }

        return next_to_try;
}

static void run_parallel(unsigned int tasks, void (*fn)(int i, void *data),
                         void *data)
{
        int next_sched_cpu = 0;
        pid_t pid[tasks];
        int i;

        for (i = 0; i < tasks; i++) {
                pid[i] = fork();
                if (pid[i] == 0) {
                        next_sched_cpu = sched_next_online(0, next_sched_cpu);
                        fn(i, data);
                        exit(0);
                } else if (pid[i] == -1) {
                        printf("couldn't spawn #%d process\n", i);
                        exit(1);
                }
                /* It is mostly redundant and just allow the parent
                 * process to update next_shced_cpu for the next child
                 * process
                 */
                next_sched_cpu = sched_next_online(pid[i], next_sched_cpu);
        }
        for (i = 0; i < tasks; i++) {
                int status;

                assert(waitpid(pid[i], &status, 0) == pid[i]);
                assert(status == 0);
        }
}

static void do_test_lru_dist(int task, void *data)
{
        unsigned int nr_misses = 0;
        struct pfect_lru pfect_lru;
        unsigned long long key, value = 1234;
        unsigned int i;

        unsigned int lru_map_fd = ((unsigned int *)data)[0];
        unsigned int lru_size = ((unsigned int *)data)[1];
        unsigned long long key_offset = task * dist_key_counts;

        pfect_lru_init(&pfect_lru, lru_size, dist_key_counts);

        for (i = 0; i < dist_key_counts; i++) {
                key = dist_keys[i] + key_offset;

                pfect_lru_lookup_or_insert(&pfect_lru, key);

                if (!bpf_map_lookup_elem(lru_map_fd, &key, &value))
                        continue;

                if (bpf_map_update_elem(lru_map_fd, &key, &value, BPF_NOEXIST)) {
                        printf("bpf_map_update_elem(lru_map_fd, %llu): errno:%d\n",
                               key, errno);
                        assert(0);
                }

                nr_misses++;
        }

        printf("    task:%d BPF LRU: nr_unique:%u(/%u) nr_misses:%u(/%u)\n",
               task, pfect_lru.nr_unique, dist_key_counts, nr_misses,
               dist_key_counts);
        printf("    task:%d Perfect LRU: nr_unique:%u(/%u) nr_misses:%u(/%u)\n",
               task, pfect_lru.nr_unique, pfect_lru.total,
               pfect_lru.nr_misses, pfect_lru.total);

        pfect_lru_destroy(&pfect_lru);
        close(lru_map_fd);
}

static void test_parallel_lru_dist(int map_type, int map_flags,
                                   int nr_tasks, unsigned int lru_size)
{
        int child_data[2];
        int lru_map_fd;

        printf("%s (map_type:%d map_flags:0x%X):\n", __func__, map_type,
               map_flags);

        if (map_flags & BPF_F_NO_COMMON_LRU)
                lru_map_fd = create_map(map_type, map_flags,
                                        nr_cpus * lru_size);
        else
                lru_map_fd = create_map(map_type, map_flags,
                                        nr_tasks * lru_size);
        assert(lru_map_fd != -1);

        child_data[0] = lru_map_fd;
        child_data[1] = lru_size;

        run_parallel(nr_tasks, do_test_lru_dist, child_data);

        close(lru_map_fd);
}

static void test_lru_loss0(int map_type, int map_flags)
{
        unsigned long long key, value[nr_cpus];
        unsigned int old_unused_losses = 0;
        unsigned int new_unused_losses = 0;
        unsigned int used_losses = 0;
        int map_fd;

        printf("%s (map_type:%d map_flags:0x%X): ", __func__, map_type,
               map_flags);

        assert(sched_next_online(0, 0) != -1);

        if (map_flags & BPF_F_NO_COMMON_LRU)
                map_fd = create_map(map_type, map_flags, 900 * nr_cpus);
        else
                map_fd = create_map(map_type, map_flags, 900);

        assert(map_fd != -1);

        value[0] = 1234;

        for (key = 1; key <= 1000; key++) {
                int start_key, end_key;

                assert(bpf_map_update_elem(map_fd, &key, value, BPF_NOEXIST) == 0);

                start_key = 101;
                end_key = min(key, 900);

                while (start_key <= end_key) {
                        bpf_map_lookup_elem(map_fd, &start_key, value);
                        start_key++;
                }
        }

        for (key = 1; key <= 1000; key++) {
                if (bpf_map_lookup_elem(map_fd, &key, value)) {
                        if (key <= 100)
                                old_unused_losses++;
                        else if (key <= 900)
                                used_losses++;
                        else
                                new_unused_losses++;
                }
        }

        close(map_fd);

        printf("older-elem-losses:%d(/100) active-elem-losses:%d(/800) "
               "newer-elem-losses:%d(/100)\n",
               old_unused_losses, used_losses, new_unused_losses);
}

static void test_lru_loss1(int map_type, int map_flags)
{
        unsigned long long key, value[nr_cpus];
        int map_fd;
        unsigned int nr_losses = 0;

        printf("%s (map_type:%d map_flags:0x%X): ", __func__, map_type,
               map_flags);

        assert(sched_next_online(0, 0) != -1);

        if (map_flags & BPF_F_NO_COMMON_LRU)
                map_fd = create_map(map_type, map_flags, 1000 * nr_cpus);
        else
                map_fd = create_map(map_type, map_flags, 1000);

        assert(map_fd != -1);

        value[0] = 1234;

        for (key = 1; key <= 1000; key++)
                assert(!bpf_map_update_elem(map_fd, &key, value, BPF_NOEXIST));

        for (key = 1; key <= 1000; key++) {
                if (bpf_map_lookup_elem(map_fd, &key, value))
                        nr_losses++;
        }

        close(map_fd);

        printf("nr_losses:%d(/1000)\n", nr_losses);
}

static void do_test_parallel_lru_loss(int task, void *data)
{
        const unsigned int nr_stable_elems = 1000;
        const unsigned int nr_repeats = 100000;

        int map_fd = *(int *)data;
        unsigned long long stable_base;
        unsigned long long key, value[nr_cpus];
        unsigned long long next_ins_key;
        unsigned int nr_losses = 0;
        unsigned int i;

        stable_base = task * nr_repeats * 2 + 1;
        next_ins_key = stable_base;
        value[0] = 1234;
        for (i = 0; i < nr_stable_elems; i++) {
                assert(bpf_map_update_elem(map_fd, &next_ins_key, value,
                                       BPF_NOEXIST) == 0);
                next_ins_key++;
        }

        for (i = 0; i < nr_repeats; i++) {
                int rn;

                rn = rand();

                if (rn % 10) {
                        key = rn % nr_stable_elems + stable_base;
                        bpf_map_lookup_elem(map_fd, &key, value);
                } else {
                        bpf_map_update_elem(map_fd, &next_ins_key, value,
                                        BPF_NOEXIST);
                        next_ins_key++;
                }
        }

        key = stable_base;
        for (i = 0; i < nr_stable_elems; i++) {
                if (bpf_map_lookup_elem(map_fd, &key, value))
                        nr_losses++;
                key++;
        }

        printf("    task:%d nr_losses:%u\n", task, nr_losses);
}

static void test_parallel_lru_loss(int map_type, int map_flags, int nr_tasks)
{
        int map_fd;

        printf("%s (map_type:%d map_flags:0x%X):\n", __func__, map_type,
               map_flags);

        /* Give 20% more than the active working set */
        if (map_flags & BPF_F_NO_COMMON_LRU)
                map_fd = create_map(map_type, map_flags,
                                    nr_cpus * (1000 + 200));
        else
                map_fd = create_map(map_type, map_flags,
                                    nr_tasks * (1000 + 200));

        assert(map_fd != -1);

        run_parallel(nr_tasks, do_test_parallel_lru_loss, &map_fd);

        close(map_fd);
}

int main(int argc, char **argv)
{
        struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
        int map_flags[] = {0, BPF_F_NO_COMMON_LRU};
        const char *dist_file;
        int nr_tasks = 1;
        int lru_size;
        int f;

        if (argc < 4) {
                printf("Usage: %s <dist-file> <lru-size> <nr-tasks>\n",
                       argv[0]);
                return -1;
        }

        dist_file = argv[1];
        lru_size = atoi(argv[2]);
        nr_tasks = atoi(argv[3]);

        setbuf(stdout, NULL);

        assert(!setrlimit(RLIMIT_MEMLOCK, &r));

        srand(time(NULL));

        nr_cpus = bpf_num_possible_cpus();
        assert(nr_cpus != -1);
        printf("nr_cpus:%d\n\n", nr_cpus);

        nr_tasks = min(nr_tasks, nr_cpus);

        dist_key_counts = read_keys(dist_file, &dist_keys);
        if (!dist_key_counts) {
                printf("%s has no key\n", dist_file);
                return -1;
        }

        for (f = 0; f < sizeof(map_flags) / sizeof(*map_flags); f++) {
                test_lru_loss0(BPF_MAP_TYPE_LRU_HASH, map_flags[f]);
                test_lru_loss1(BPF_MAP_TYPE_LRU_HASH, map_flags[f]);
                test_parallel_lru_loss(BPF_MAP_TYPE_LRU_HASH, map_flags[f],
                                       nr_tasks);
                test_parallel_lru_dist(BPF_MAP_TYPE_LRU_HASH, map_flags[f],
                                       nr_tasks, lru_size);
                printf("\n");
        }

        free(dist_keys);

        return 0;
}