/*
 *
 * A test for the patch "Allow compaction of unevictable pages".
 * With this patch we should be able to allocate at least 1/4
 * of RAM in huge pages. Without the patch much less is
 * allocated.
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/resource.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>

#define MAP_SIZE 1048576

struct map_list {
        void *map;
        struct map_list *next;
};

int read_memory_info(unsigned long *memfree, unsigned long *hugepagesize)
{
        char  buffer[256] = {0};
        char *cmd = "cat /proc/meminfo | grep -i memfree | grep -o '[0-9]*'";
        FILE *cmdfile = popen(cmd, "r");

        if (!(fgets(buffer, sizeof(buffer), cmdfile))) {
                perror("Failed to read meminfo\n");
                return -1;
        }

        pclose(cmdfile);

        *memfree = atoll(buffer);
        cmd = "cat /proc/meminfo | grep -i hugepagesize | grep -o '[0-9]*'";
        cmdfile = popen(cmd, "r");

        if (!(fgets(buffer, sizeof(buffer), cmdfile))) {
                perror("Failed to read meminfo\n");
                return -1;
        }

        pclose(cmdfile);
        *hugepagesize = atoll(buffer);

        return 0;
}

int prereq(void)
{
        char allowed;
        int fd;

        fd = open("/proc/sys/vm/compact_unevictable_allowed",
                  O_RDONLY | O_NONBLOCK);
        if (fd < 0) {
                perror("Failed to open\n"
                       "/proc/sys/vm/compact_unevictable_allowed\n");
                return -1;
        }

        if (read(fd, &allowed, sizeof(char)) != sizeof(char)) {
                perror("Failed to read from\n"
                       "/proc/sys/vm/compact_unevictable_allowed\n");
                close(fd);
                return -1;
        }

        close(fd);
        if (allowed == '1')
                return 0;

        return -1;
}

int check_compaction(unsigned long mem_free, unsigned int hugepage_size)
{
        int fd;
        int compaction_index = 0;
        char initial_nr_hugepages[10] = {0};
        char nr_hugepages[10] = {0};

        /* We want to test with 80% of available memory. Else, OOM killer comes
           in to play */
        mem_free = mem_free * 0.8;

        fd = open("/proc/sys/vm/nr_hugepages", O_RDWR | O_NONBLOCK);
        if (fd < 0) {
                perror("Failed to open /proc/sys/vm/nr_hugepages");
                return -1;
        }

        if (read(fd, initial_nr_hugepages, sizeof(initial_nr_hugepages)) <= 0) {
                perror("Failed to read from /proc/sys/vm/nr_hugepages");
                goto close_fd;
        }

        /* Start with the initial condition of 0 huge pages*/
        if (write(fd, "0", sizeof(char)) != sizeof(char)) {
                perror("Failed to write 0 to /proc/sys/vm/nr_hugepages\n");
                goto close_fd;
        }

        lseek(fd, 0, SEEK_SET);

        /* Request a large number of huge pages. The Kernel will allocate
           as much as it can */
        if (write(fd, "100000", (6*sizeof(char))) != (6*sizeof(char))) {
                perror("Failed to write 100000 to /proc/sys/vm/nr_hugepages\n");
                goto close_fd;
        }

        lseek(fd, 0, SEEK_SET);

        if (read(fd, nr_hugepages, sizeof(nr_hugepages)) <= 0) {
                perror("Failed to re-read from /proc/sys/vm/nr_hugepages\n");
                goto close_fd;
        }

        /* We should have been able to request at least 1/3 rd of the memory in
           huge pages */
        compaction_index = mem_free/(atoi(nr_hugepages) * hugepage_size);

        if (compaction_index > 3) {
                printf("No of huge pages allocated = %d\n",
                       (atoi(nr_hugepages)));
                fprintf(stderr, "ERROR: Less that 1/%d of memory is available\n"
                        "as huge pages\n", compaction_index);
                goto close_fd;
        }

        printf("No of huge pages allocated = %d\n",
               (atoi(nr_hugepages)));

        if (write(fd, initial_nr_hugepages, strlen(initial_nr_hugepages))
            != strlen(initial_nr_hugepages)) {
                perror("Failed to write value to /proc/sys/vm/nr_hugepages\n");
                goto close_fd;
        }

        close(fd);
        return 0;

 close_fd:
        close(fd);
        printf("Not OK. Compaction test failed.");
        return -1;
}


int main(int argc, char **argv)
{
        struct rlimit lim;
        struct map_list *list, *entry;
        size_t page_size, i;
        void *map = NULL;
        unsigned long mem_free = 0;
        unsigned long hugepage_size = 0;
        unsigned long mem_fragmentable = 0;

        if (prereq() != 0) {
                printf("Either the sysctl compact_unevictable_allowed is not\n"
                       "set to 1 or couldn't read the proc file.\n"
                       "Skipping the test\n");
                return 0;
        }

        lim.rlim_cur = RLIM_INFINITY;
        lim.rlim_max = RLIM_INFINITY;
        if (setrlimit(RLIMIT_MEMLOCK, &lim)) {
                perror("Failed to set rlimit:\n");
                return -1;
        }

        page_size = getpagesize();

        list = NULL;

        if (read_memory_info(&mem_free, &hugepage_size) != 0) {
                printf("ERROR: Cannot read meminfo\n");
                return -1;
        }

        mem_fragmentable = mem_free * 0.8 / 1024;

        while (mem_fragmentable > 0) {
                map = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE,
                           MAP_ANONYMOUS | MAP_PRIVATE | MAP_LOCKED, -1, 0);
                if (map == MAP_FAILED)
                        break;

                entry = malloc(sizeof(struct map_list));
                if (!entry) {
                        munmap(map, MAP_SIZE);
                        break;
                }
                entry->map = map;
                entry->next = list;
                list = entry;

                /* Write something (in this case the address of the map) to
                 * ensure that KSM can't merge the mapped pages
                 */
                for (i = 0; i < MAP_SIZE; i += page_size)
                        *(unsigned long *)(map + i) = (unsigned long)map + i;

                mem_fragmentable--;
        }

        for (entry = list; entry != NULL; entry = entry->next) {
                munmap(entry->map, MAP_SIZE);
                if (!entry->next)
                        break;
                entry = entry->next;
        }

        if (check_compaction(mem_free, hugepage_size) == 0)
                return 0;

        return -1;
}