/* Start/stop KSM, for systemd.

 * Copyright (C) 2009, 2011 Red Hat, Inc.

 * Written by Paolo Bonzini <pbonzini@redhat.com>.

 * Based on the original sysvinit script by Dan Kenigsberg <danken@redhat.com>

 * This file is distributed under the GNU General Public License, version 2

 * or later.  */

#include <unistd.h>

#include <stdio.h>

#include <limits.h>

#include <stdint.h>

#include <stdlib.h>

#include <string.h>

#define KSM_MAX_KERNEL_PAGES_FILE "/sys/kernel/mm/ksm/max_kernel_pages"

#define KSM_RUN_FILE		  "/sys/kernel/mm/ksm/run"

char *program_name;

int usage(void)

{

	fprintf(stderr, "Usage: %s {start|stop}\n", program_name);

	return 1;

}

int write_value(uint64_t value, char *filename)

{

	FILE *fp;

	if (!(fp = fopen(filename, "w")) ||

	    fprintf(fp, "%llu\n", (unsigned long long) value) == EOF ||

	    fflush(fp) == EOF ||

	    fclose(fp) == EOF)

		return 1;

	return 0;

}

uint64_t ksm_max_kernel_pages()

{

	char *var = getenv("KSM_MAX_KERNEL_PAGES");

	char *endptr;

	uint64_t value;

	if (var && *var) {

		value = strtoll(var, &endptr, 0);

		if (value < LLONG_MAX && !*endptr)

			return value;

	}

	/* Unless KSM_MAX_KERNEL_PAGES is set, let KSM munch up to half of

	 * total memory.  */

	return sysconf(_SC_PHYS_PAGES) / 2;

}

int start(void)

{

	if (access(KSM_MAX_KERNEL_PAGES_FILE, R_OK) >= 0)

		write_value(ksm_max_kernel_pages(), KSM_MAX_KERNEL_PAGES_FILE);

	return write_value(1, KSM_RUN_FILE);

}

int stop(void)

{

	return write_value(0, KSM_RUN_FILE);

}

int main(int argc, char **argv)

{

	program_name = argv[0];

	if (argc < 2) {

		return usage();

	} else if (!strcmp(argv[1], "start")) {

		return start();

	} else if (!strcmp(argv[1], "stop")) {

		return stop();

	} else {

		return usage();

	}

}