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/* Start/stop KSM, for systemd.
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 * Copyright (C) 2009, 2011 Red Hat, Inc.
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 * Written by Paolo Bonzini <pbonzini@redhat.com>.
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 * Based on the original sysvinit script by Dan Kenigsberg <danken@redhat.com>
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 * This file is distributed under the GNU General Public License, version 2
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 * or later.  */
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#include <unistd.h>
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#include <stdio.h>
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#include <limits.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#define KSM_MAX_KERNEL_PAGES_FILE "/sys/kernel/mm/ksm/max_kernel_pages"
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#define KSM_RUN_FILE		  "/sys/kernel/mm/ksm/run"
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char *program_name;
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int usage(void)
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{
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	fprintf(stderr, "Usage: %s {start|stop}\n", program_name);
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	return 1;
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}
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int write_value(uint64_t value, char *filename)
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{
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	FILE *fp;
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	if (!(fp = fopen(filename, "w")) ||
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	    fprintf(fp, "%llu\n", (unsigned long long) value) == EOF ||
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	    fflush(fp) == EOF ||
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	    fclose(fp) == EOF)
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		return 1;
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	return 0;
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}
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uint64_t ksm_max_kernel_pages()
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{
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	char *var = getenv("KSM_MAX_KERNEL_PAGES");
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	char *endptr;
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	uint64_t value;
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	if (var && *var) {
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		value = strtoll(var, &endptr, 0);
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		if (value < LLONG_MAX && !*endptr)
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			return value;
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	}
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	/* Unless KSM_MAX_KERNEL_PAGES is set, let KSM munch up to half of
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	 * total memory.  */
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	return sysconf(_SC_PHYS_PAGES) / 2;
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}
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int start(void)
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{
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	if (access(KSM_MAX_KERNEL_PAGES_FILE, R_OK) >= 0)
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		write_value(ksm_max_kernel_pages(), KSM_MAX_KERNEL_PAGES_FILE);
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	return write_value(1, KSM_RUN_FILE);
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}
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int stop(void)
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{
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	return write_value(0, KSM_RUN_FILE);
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}
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int main(int argc, char **argv)
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{
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	program_name = argv[0];
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	if (argc < 2) {
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		return usage();
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	} else if (!strcmp(argv[1], "start")) {
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		return start();
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	} else if (!strcmp(argv[1], "stop")) {
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		return stop();
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	} else {
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		return usage();
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	}
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}