| /* |
| * SPDX-License-Identifier: MIT |
| * |
| * Copyright © 2014-2016 Intel Corporation |
| */ |
| |
| #include <linux/jiffies.h> |
| |
| #include <drm/drm_file.h> |
| |
| #include "i915_drv.h" |
| #include "i915_gem_ioctls.h" |
| #include "i915_gem_object.h" |
| |
| /* |
| * 20ms is a fairly arbitrary limit (greater than the average frame time) |
| * chosen to prevent the CPU getting more than a frame ahead of the GPU |
| * (when using lax throttling for the frontbuffer). We also use it to |
| * offer free GPU waitboosts for severely congested workloads. |
| */ |
| #define DRM_I915_THROTTLE_JIFFIES msecs_to_jiffies(20) |
| |
| /* |
| * Throttle our rendering by waiting until the ring has completed our requests |
| * emitted over 20 msec ago. |
| * |
| * Note that if we were to use the current jiffies each time around the loop, |
| * we wouldn't escape the function with any frames outstanding if the time to |
| * render a frame was over 20ms. |
| * |
| * This should get us reasonable parallelism between CPU and GPU but also |
| * relatively low latency when blocking on a particular request to finish. |
| */ |
| int |
| i915_gem_throttle_ioctl(struct drm_device *dev, void *data, |
| struct drm_file *file) |
| { |
| struct drm_i915_file_private *file_priv = file->driver_priv; |
| unsigned long recent_enough = jiffies - DRM_I915_THROTTLE_JIFFIES; |
| struct i915_request *request, *target = NULL; |
| long ret; |
| |
| /* ABI: return -EIO if already wedged */ |
| ret = intel_gt_terminally_wedged(&to_i915(dev)->gt); |
| if (ret) |
| return ret; |
| |
| spin_lock(&file_priv->mm.lock); |
| list_for_each_entry(request, &file_priv->mm.request_list, client_link) { |
| if (time_after_eq(request->emitted_jiffies, recent_enough)) |
| break; |
| |
| if (target && xchg(&target->file_priv, NULL)) |
| list_del(&target->client_link); |
| |
| target = request; |
| } |
| if (target) |
| i915_request_get(target); |
| spin_unlock(&file_priv->mm.lock); |
| |
| if (!target) |
| return 0; |
| |
| ret = i915_request_wait(target, |
| I915_WAIT_INTERRUPTIBLE, |
| MAX_SCHEDULE_TIMEOUT); |
| i915_request_put(target); |
| |
| return ret < 0 ? ret : 0; |
| } |