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* x86_energy_perf_policy -- set the energy versus performance
* policy preference bias on recent X86 processors.
*/
/*
* Copyright (c) 2010, Intel Corporation.
* Len Brown <len.brown@intel.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/resource.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/time.h>
#include <stdlib.h>
#include <string.h>
unsigned int verbose; /* set with -v */
unsigned int read_only; /* set with -r */
char *progname;
unsigned long long new_bias;
int cpu = -1;
/*
* Usage:
*
* -c cpu: limit action to a single CPU (default is all CPUs)
* -v: verbose output (can invoke more than once)
* -r: read-only, don't change any settings
*
* performance
* Performance is paramount.
* Unwilling to sacrifice any performance
* for the sake of energy saving. (hardware default)
*
* normal
* Can tolerate minor performance compromise
* for potentially significant energy savings.
* (reasonable default for most desktops and servers)
*
* powersave
* Can tolerate significant performance hit
* to maximize energy savings.
*
* n
* a numerical value to write to the underlying MSR.
*/
void usage(void)
{
printf("%s: [-c cpu] [-v] "
"(-r | 'performance' | 'normal' | 'powersave' | n)\n",
progname);
exit(1);
}
#define MSR_IA32_ENERGY_PERF_BIAS 0x000001b0
#define BIAS_PERFORMANCE 0
#define BIAS_BALANCE 6
#define BIAS_POWERSAVE 15
void cmdline(int argc, char **argv)
{
int opt;
progname = argv[0];
while ((opt = getopt(argc, argv, "+rvc:")) != -1) {
switch (opt) {
case 'c':
cpu = atoi(optarg);
break;
case 'r':
read_only = 1;
break;
case 'v':
verbose++;
break;
default:
usage();
}
}
/* if -r, then should be no additional optind */
if (read_only && (argc > optind))
usage();
/*
* if no -r , then must be one additional optind
*/
if (!read_only) {
if (argc != optind + 1) {
printf("must supply -r or policy param\n");
usage();
}
if (!strcmp("performance", argv[optind])) {
new_bias = BIAS_PERFORMANCE;
} else if (!strcmp("normal", argv[optind])) {
new_bias = BIAS_BALANCE;
} else if (!strcmp("powersave", argv[optind])) {
new_bias = BIAS_POWERSAVE;
} else {
char *endptr;
new_bias = strtoull(argv[optind], &endptr, 0);
if (endptr == argv[optind] ||
new_bias > BIAS_POWERSAVE) {
fprintf(stderr, "invalid value: %s\n",
argv[optind]);
usage();
}
}
}
}
/*
* validate_cpuid()
* returns on success, quietly exits on failure (make verbose with -v)
*/
void validate_cpuid(void)
{
unsigned int eax, ebx, ecx, edx, max_level;
unsigned int fms, family, model, stepping;
eax = ebx = ecx = edx = 0;
asm("cpuid" : "=a" (max_level), "=b" (ebx), "=c" (ecx),
"=d" (edx) : "a" (0));
if (ebx != 0x756e6547 || edx != 0x49656e69 || ecx != 0x6c65746e) {
if (verbose)
fprintf(stderr, "%.4s%.4s%.4s != GenuineIntel",
(char *)&ebx, (char *)&edx, (char *)&ecx);
exit(1);
}
asm("cpuid" : "=a" (fms), "=c" (ecx), "=d" (edx) : "a" (1) : "ebx");
family = (fms >> 8) & 0xf;
model = (fms >> 4) & 0xf;
stepping = fms & 0xf;
if (family == 6 || family == 0xf)
model += ((fms >> 16) & 0xf) << 4;
if (verbose > 1)
printf("CPUID %d levels family:model:stepping "
"0x%x:%x:%x (%d:%d:%d)\n", max_level,
family, model, stepping, family, model, stepping);
if (!(edx & (1 << 5))) {
if (verbose)
printf("CPUID: no MSR\n");
exit(1);
}
/*
* Support for MSR_IA32_ENERGY_PERF_BIAS
* is indicated by CPUID.06H.ECX.bit3
*/
asm("cpuid" : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx) : "a" (6));
if (verbose)
printf("CPUID.06H.ECX: 0x%x\n", ecx);
if (!(ecx & (1 << 3))) {
if (verbose)
printf("CPUID: No MSR_IA32_ENERGY_PERF_BIAS\n");
exit(1);
}
return; /* success */
}
unsigned long long get_msr(int cpu, int offset)
{
unsigned long long msr;
char msr_path[32];
int retval;
int fd;
sprintf(msr_path, "/dev/cpu/%d/msr", cpu);
fd = open(msr_path, O_RDONLY);
if (fd < 0) {
printf("Try \"# modprobe msr\"\n");
perror(msr_path);
exit(1);
}
retval = pread(fd, &msr, sizeof msr, offset);
if (retval != sizeof msr) {
printf("pread cpu%d 0x%x = %d\n", cpu, offset, retval);
exit(-2);
}
close(fd);
return msr;
}
unsigned long long put_msr(int cpu, unsigned long long new_msr, int offset)
{
unsigned long long old_msr;
char msr_path[32];
int retval;
int fd;
sprintf(msr_path, "/dev/cpu/%d/msr", cpu);
fd = open(msr_path, O_RDWR);
if (fd < 0) {
perror(msr_path);
exit(1);
}
retval = pread(fd, &old_msr, sizeof old_msr, offset);
if (retval != sizeof old_msr) {
perror("pwrite");
printf("pread cpu%d 0x%x = %d\n", cpu, offset, retval);
exit(-2);
}
retval = pwrite(fd, &new_msr, sizeof new_msr, offset);
if (retval != sizeof new_msr) {
perror("pwrite");
printf("pwrite cpu%d 0x%x = %d\n", cpu, offset, retval);
exit(-2);
}
close(fd);
return old_msr;
}
void print_msr(int cpu)
{
printf("cpu%d: 0x%016llx\n",
cpu, get_msr(cpu, MSR_IA32_ENERGY_PERF_BIAS));
}
void update_msr(int cpu)
{
unsigned long long previous_msr;
previous_msr = put_msr(cpu, new_bias, MSR_IA32_ENERGY_PERF_BIAS);
if (verbose)
printf("cpu%d msr0x%x 0x%016llx -> 0x%016llx\n",
cpu, MSR_IA32_ENERGY_PERF_BIAS, previous_msr, new_bias);
return;
}
char *proc_stat = "/proc/stat";
/*
* run func() on every cpu in /dev/cpu
*/
void for_every_cpu(void (func)(int))
{
FILE *fp;
int retval;
fp = fopen(proc_stat, "r");
if (fp == NULL) {
perror(proc_stat);
exit(1);
}
retval = fscanf(fp, "cpu %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n");
if (retval != 0) {
perror("/proc/stat format");
exit(1);
}
while (1) {
int cpu;
retval = fscanf(fp,
"cpu%u %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n",
&cpu);
if (retval != 1)
return;
func(cpu);
}
fclose(fp);
}
int main(int argc, char **argv)
{
cmdline(argc, argv);
if (verbose > 1)
printf("x86_energy_perf_policy Nov 24, 2010"
" - Len Brown <lenb@kernel.org>\n");
if (verbose > 1 && !read_only)
printf("new_bias %lld\n", new_bias);
validate_cpuid();
if (cpu != -1) {
if (read_only)
print_msr(cpu);
else
update_msr(cpu);
} else {
if (read_only)
for_every_cpu(print_msr);
else
for_every_cpu(update_msr);
}
return 0;
}
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