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Commit 36229897 authored by Len Brown's avatar Len Brown
Browse files

tools/power turbostat: make fewer systems calls 



skip the open(2)/close(2) on each msr read
by keeping the /dev/cpu/*/msr files open.

The remaining read(2) is generally far fewer cycles
than the removed open(2) system call.

Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent 58cc30a4

tools/power/x86/turbostat/turbostat.c

+41 −10
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ 


char *proc_stat = "/proc/stat";

FILE *outf;

int *fd_percpu;

struct timespec interval_ts = {5, 0};

unsigned int debug;

unsigned int rapl_joules;
@@ -270,23 +271,34 @@ int cpu_migrate(int cpu) 
	else

		return 0;

}



int get_msr(int cpu, off_t offset, unsigned long long *msr)

int get_msr_fd(int cpu)

{

	ssize_t retval;

	char pathname[32];

	int fd;



	fd = fd_percpu[cpu];



	if (fd)

		return fd;



	sprintf(pathname, "/dev/cpu/%d/msr", cpu);

	fd = open(pathname, O_RDONLY);

	if (fd < 0)

		err(-1, "%s open failed, try chown or chmod +r /dev/cpu/*/msr, or run as root", pathname);



	retval = pread(fd, msr, sizeof *msr, offset);

	close(fd);

	fd_percpu[cpu] = fd;



	return fd;

}



int get_msr(int cpu, off_t offset, unsigned long long *msr)

{

	ssize_t retval;



	retval = pread(get_msr_fd(cpu), msr, sizeof(*msr), offset);



	if (retval != sizeof *msr)

		err(-1, "%s offset 0x%llx read failed", pathname, (unsigned long long)offset);

		err(-1, "msr %d offset 0x%llx read failed", cpu, (unsigned long long)offset);



	return 0;

}
@@ -1460,12 +1472,23 @@ dump_config_tdp(void) 
	fprintf(outf, " lock=%d", (unsigned int)(msr >> 31) & 1);

	fprintf(outf, ")\n");

}

void free_fd_percpu(void)

{

	int i;



	for (i = 0; i < topo.max_cpu_num; ++i) {

		if (fd_percpu[i] != 0)

			close(fd_percpu[i]);

	}



	free(fd_percpu);

}



void free_all_buffers(void)

{

	CPU_FREE(cpu_present_set);

	cpu_present_set = NULL;

	cpu_present_set = 0;

	cpu_present_setsize = 0;



	CPU_FREE(cpu_affinity_set);

	cpu_affinity_set = NULL;
@@ -1490,6 +1513,8 @@ void free_all_buffers(void) 
	free(output_buffer);

	output_buffer = NULL;

	outp = NULL;



	free_fd_percpu();

}



/*
@@ -3202,10 +3227,16 @@ void allocate_output_buffer() 
	if (outp == NULL)

		err(-1, "calloc output buffer");

}



void allocate_fd_percpu(void)

{

	fd_percpu = calloc(topo.max_cpu_num, sizeof(int));

	if (fd_percpu == NULL)

		err(-1, "calloc fd_percpu");

}

void setup_all_buffers(void)

{

	topology_probe();

	allocate_fd_percpu();

	allocate_counters(&thread_even, &core_even, &package_even);

	allocate_counters(&thread_odd, &core_odd, &package_odd);

	allocate_output_buffer();