1 /* 2 * SPDX-License-Identifier: MIT 3 * 4 * Copyright © 2014-2016 Intel Corporation 5 */ 6 7 #include <linux/jiffies.h> 8 9 #include <drm/drm_file.h> 10 11 #include "i915_drv.h" 12 #include "i915_file_private.h" 13 #include "i915_gem_context.h" 14 #include "i915_gem_ioctls.h" 15 #include "i915_gem_object.h" 16 17 /* 18 * 20ms is a fairly arbitrary limit (greater than the average frame time) 19 * chosen to prevent the CPU getting more than a frame ahead of the GPU 20 * (when using lax throttling for the frontbuffer). We also use it to 21 * offer free GPU waitboosts for severely congested workloads. 22 */ 23 #define DRM_I915_THROTTLE_JIFFIES msecs_to_jiffies(20) 24 25 /* 26 * Throttle our rendering by waiting until the ring has completed our requests 27 * emitted over 20 msec ago. 28 * 29 * Note that if we were to use the current jiffies each time around the loop, 30 * we wouldn't escape the function with any frames outstanding if the time to 31 * render a frame was over 20ms. 32 * 33 * This should get us reasonable parallelism between CPU and GPU but also 34 * relatively low latency when blocking on a particular request to finish. 35 */ 36 int 37 i915_gem_throttle_ioctl(struct drm_device *dev, void *data, 38 struct drm_file *file) 39 { 40 const unsigned long recent_enough = jiffies - DRM_I915_THROTTLE_JIFFIES; 41 struct drm_i915_file_private *file_priv = file->driver_priv; 42 struct drm_i915_private *i915 = to_i915(dev); 43 struct i915_gem_context *ctx; 44 unsigned long idx; 45 long ret; 46 47 /* ABI: return -EIO if already wedged */ 48 ret = intel_gt_terminally_wedged(to_gt(i915)); 49 if (ret) 50 return ret; 51 52 rcu_read_lock(); 53 xa_for_each(&file_priv->context_xa, idx, ctx) { 54 struct i915_gem_engines_iter it; 55 struct intel_context *ce; 56 57 if (!kref_get_unless_zero(&ctx->ref)) 58 continue; 59 rcu_read_unlock(); 60 61 for_each_gem_engine(ce, 62 i915_gem_context_lock_engines(ctx), 63 it) { 64 struct i915_request *rq, *target = NULL; 65 66 if (!ce->timeline) 67 continue; 68 69 mutex_lock(&ce->timeline->mutex); 70 list_for_each_entry_reverse(rq, 71 &ce->timeline->requests, 72 link) { 73 if (i915_request_completed(rq)) 74 break; 75 76 if (time_after(rq->emitted_jiffies, 77 recent_enough)) 78 continue; 79 80 target = i915_request_get(rq); 81 break; 82 } 83 mutex_unlock(&ce->timeline->mutex); 84 if (!target) 85 continue; 86 87 ret = i915_request_wait(target, 88 I915_WAIT_INTERRUPTIBLE, 89 MAX_SCHEDULE_TIMEOUT); 90 i915_request_put(target); 91 if (ret < 0) 92 break; 93 } 94 i915_gem_context_unlock_engines(ctx); 95 i915_gem_context_put(ctx); 96 97 rcu_read_lock(); 98 } 99 rcu_read_unlock(); 100 101 return ret < 0 ? ret : 0; 102 } 103