rpi_gpu_usage_monitor.cpp

#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/ioctl.h>


#ifdef USE_TEST_FILE
static const char* reg_file = "junk/v3d_test_file";
#else
static const char* reg_file = "/debug/dri/0/v3d_regs";
#endif

static char file_buf[4096];

static const char* set0name0 = "CT0CA";
static const char* set0name1 = "CT0EA";
static const char* set1name0 = "CT1CA";
static const char* set1name1 = "CT1EA";

char* set0name0_location = 0;
char* set0name1_location = 0;
char* set1name0_location = 0;
char* set1name1_location = 0;

#define _scan(name) __scan(name, name ## _location, c) 
static void __scan(const char*name, char*&location, char*c) {
    if (strncmp(c, name, 5)==0) {
        assert(!location);
        location = c + 18;
        assert(*(location - 4)== ':');
        assert(*(location - 1)== 'x');
        assert(*(location + 8)=='\n');
    }
}

int main () {
    
    auto reg_f = open(reg_file, O_RDONLY);
    if (reg_f == -1) {
        fprintf(stderr, "Could not open %s (%s)\n", reg_file, strerror(errno));
        fprintf(stderr, "Maybe you need to run as root or run:\n");
        fprintf(stderr, "  sudo mount -t debugfs none /debug\n");
        exit(-1);
    }
    
    
    
    
    int columns;
    {
        struct winsize ws;
        auto r1 = ioctl(1, TIOCGWINSZ, &ws);
        
        if (isatty(1) && !r1) {
            columns = ws.ws_col;
        } else {
            fprintf(stderr, "Couldn't determine terminal width\n");
            columns = 20;
        }
    }
    
    auto reg_f_size = read(reg_f, file_buf, sizeof file_buf);
    assert(reg_f_size >=0);
    
    
    // V3D_BPCS (0x0304): 0xdeadbeef$
    
    for(char*c = file_buf; c<file_buf+reg_f_size; c++) {
        
        _scan(set0name0);
        _scan(set0name1);
        _scan(set1name0);
        _scan(set1name1);
    }
    
    assert(set0name0_location);
    assert(set0name1_location);
    assert(set1name0_location);
    assert(set1name1_location);
    
    for (;;) {
        
        static const int counts_total = 100;
        int counts_idle   = 0;
        
        for(int count_i=0; count_i < counts_total; count_i++) {
            
            if ((memcmp(set0name0_location, set0name1_location, 8) == 0) &&
                (memcmp(set1name0_location, set1name1_location, 8) == 0)) {
                
                counts_idle++;
            } 
            
            auto r1 = lseek(reg_f, 0, SEEK_SET);
            assert(!r1);
            auto reg_f_size2 = read(reg_f, file_buf, sizeof file_buf);
            assert(reg_f_size2==reg_f_size);
            
            usleep(1000*1);
            
        }
        
        float   ratio_active = (float)(counts_total-counts_idle)/(float)counts_total;
        int   columns_active = (float)(columns - 8)*ratio_active;
        int   percent_active =        100.0  *ratio_active;
        
        printf("%3d%%: ", percent_active);
        for (int i=0;i<columns_active;i++) {
            putchar('#');
        }
        putchar('\n');
        fflush(stdout);
        
    }
}