Get memory usage from i915 drivers

i915_mem_usage.c

#include <assert.h>
#include <drm/drm.h>
#include <drm/i915_drm.h>
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <unistd.h>

// Copied from https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/src/intel/common/intel_gem.h
static inline int intel_ioctl(int fd, unsigned long request, void *arg) {
  int ret;

  do {
    ret = ioctl(fd, request, arg);
  } while (ret == -1 && (errno == EINTR || errno == EAGAIN));
  return ret;
}
// End Copy

// Copied from https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/src/intel/common/i915/intel_gem.h
static inline int intel_i915_query(int fd, uint64_t query_id, void *buffer, int32_t *buffer_len) {
  struct drm_i915_query_item item = {
      .query_id = query_id,
      .length = *buffer_len,
      .flags = 0,
      .data_ptr = (uintptr_t)buffer,
  };

  struct drm_i915_query args = {
      .num_items = 1,
      .flags = 0,
      .items_ptr = (uintptr_t)&item,
  };

  int ret = intel_ioctl(fd, DRM_IOCTL_I915_QUERY, &args);
  if (ret != 0)
    return -errno;
  else if (item.length < 0)
    return item.length;

  *buffer_len = item.length;
  return 0;
}

static inline void *intel_i915_query_alloc(int fd, uint64_t query_id, int32_t *query_length) {
  if (query_length)
    *query_length = 0;

  int32_t length = 0;
  int ret = intel_i915_query(fd, query_id, NULL, &length);
  if (ret < 0)
    return NULL;

  void *data = calloc(1, length);
  assert(data != NULL); /* This shouldn't happen in practice */
  if (data == NULL)
    return NULL;

  ret = intel_i915_query(fd, query_id, data, &length);
  assert(ret == 0); /* We should have caught the error above */
  if (ret < 0) {
    free(data);
    return NULL;
  }

  if (query_length)
    *query_length = length;

  return data;
}
// End Copy

int main() {
  int fd = open("/dev/dri/card0", O_WRONLY);
  if (fd < 0) {
    perror("Failed to open /dev/dri/card0");
    return 1;
  }
  struct drm_i915_query_memory_regions *regions;

  int32_t length = 0;
  regions = intel_i915_query_alloc(fd, DRM_I915_QUERY_MEMORY_REGIONS, &length);

  printf("Length of the blob: %d\n", length);
  printf("Number of regions: %d\n", regions->num_regions);

  for (size_t i = 0; i < regions->num_regions; i++) {
    struct drm_i915_memory_region_info mr = regions->regions[i];
    printf("Region %d\n", i);
    printf("Class: %d\n", mr.region.memory_class);
    printf("Instance: %d\n", mr.region.memory_instance);
    printf("Probed size: %llu KB\n", mr.probed_size);
    printf("Unallocated size: %llu KB\n", mr.unallocated_size);
  }

  close(fd);
  return 0;
}