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
i915_gem_throttle_ioctl(struct drm_device * dev,void * data,struct drm_file * file)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