How to obtain RPM value for the fans ? about gpustat

[wookayin]

We are using nvmlDeviceGetFanSpeed, but another API nvmlUnitGetFanSpeedInfo seems to allow reading of RPM values.

• https://docs.nvidia.com/deploy/nvml-api/group__nvmlUnitQueries.html#group__nvmlUnitQueries_1gf8d512cb5764d671c8bd6b0ef32ae456
• https://docs.nvidia.com/deploy/nvml-api/structnvmlUnitFanSpeeds__t.html#structnvmlUnitFanSpeeds__t

[ricciolino]

I already tried it but it does not seem to work in my case (RTX 3080). I got an "Invalid argument" exception. I guess it is only intended to be used with a specific class of GPU models (S-class unit).

So finally I was able to compile a simple snippet of C code to get what I wanted.
I exploit the NVCtrl library.
Check this thread (me author) on ubuntuforums.
Here is the snippet:

/*

Compile:
gcc -o get_GPU_fan_RPM_values get_GPU_fan_RPM_values.c -lX11 -lXNVCtrl

Usage:
./get_GPU_fan_RPM_values <fan_id>

*/


#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <X11/Xlib.h>
#include <NVCtrl/NVCtrl.h>
#include <NVCtrl/NVCtrlLib.h>

static Display *display;

static double get_att(int target, int id, int att)
{
	Bool res;
	int temp;

	res = XNVCTRLQueryTargetAttribute(display, target, id, 0, att, &temp);

	if (res == True)
		return temp;

	return -1;
}

void nvidia_cleanup(void)
{
	if (display) {
		XCloseDisplay(display);
		display = NULL;
	}
}

bool isFanId(char number[])
{
    int i = 0;
    if (number[0] == '-')
        return false;
    for (; number[i] != 0; i++)
    {
        if (number[i] > '1' || number[i] < '0')
            return false;
    }
    return true;
}

int main(int argc, char** argv) {

    if ( !(argc == 2) ) {
		printf("Please, provide the fan ID.\n");
		return 1;
    }
    if ( !isFanId(argv[1]) ) {
		printf("There is no fan with ID %d.\n", atoi(argv[1]));
		return 1;
    }

    int fanId = atoi(argv[1]);

	display = XOpenDisplay(NULL);

    if (!display) {
		printf("Cannot open connection to X11 server.\n");
        nvidia_cleanup();
		return 1;
	}

	int evt, err;
	if (!XNVCTRLQueryExtension(display, &evt, &err)) {
		printf("XNVCTRLQueryExtension error %d (evt %d).\n", err, evt);
        nvidia_cleanup();
		return 1;
    }

    printf("%d\n", (int)get_att(NV_CTRL_TARGET_TYPE_COOLER, fanId, NV_CTRL_THERMAL_COOLER_SPEED));

    nvidia_cleanup();
    
    return 0;
}