1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5// This file contains the implementation of the command buffer helper class.
6
7#include "gpu/command_buffer/client/cmd_buffer_helper.h"
8
9#include "base/logging.h"
10#include "base/time/time.h"
11#include "gpu/command_buffer/common/command_buffer.h"
12#include "gpu/command_buffer/common/trace_event.h"
13
14namespace gpu {
15
16CommandBufferHelper::CommandBufferHelper(CommandBuffer* command_buffer)
17    : command_buffer_(command_buffer),
18      ring_buffer_id_(-1),
19      ring_buffer_size_(0),
20      entries_(NULL),
21      total_entry_count_(0),
22      immediate_entry_count_(0),
23      token_(0),
24      put_(0),
25      last_put_sent_(0),
26#if defined(CMD_HELPER_PERIODIC_FLUSH_CHECK)
27      commands_issued_(0),
28#endif
29      usable_(true),
30      context_lost_(false),
31      flush_automatically_(true),
32      flush_generation_(0) {
33}
34
35void CommandBufferHelper::SetAutomaticFlushes(bool enabled) {
36  flush_automatically_ = enabled;
37  CalcImmediateEntries(0);
38}
39
40bool CommandBufferHelper::IsContextLost() {
41  if (!context_lost_) {
42    context_lost_ = error::IsError(command_buffer()->GetLastError());
43  }
44  return context_lost_;
45}
46
47void CommandBufferHelper::CalcImmediateEntries(int waiting_count) {
48  DCHECK_GE(waiting_count, 0);
49
50  // Check if usable & allocated.
51  if (!usable() || !HaveRingBuffer()) {
52    immediate_entry_count_ = 0;
53    return;
54  }
55
56  // Get maximum safe contiguous entries.
57  const int32 curr_get = get_offset();
58  if (curr_get > put_) {
59    immediate_entry_count_ = curr_get - put_ - 1;
60  } else {
61    immediate_entry_count_ =
62        total_entry_count_ - put_ - (curr_get == 0 ? 1 : 0);
63  }
64
65  // Limit entry count to force early flushing.
66  if (flush_automatically_) {
67    int32 limit =
68        total_entry_count_ /
69        ((curr_get == last_put_sent_) ? kAutoFlushSmall : kAutoFlushBig);
70
71    int32 pending =
72        (put_ + total_entry_count_ - last_put_sent_) % total_entry_count_;
73
74    if (pending > 0 && pending >= limit) {
75      // Time to force flush.
76      immediate_entry_count_ = 0;
77    } else {
78      // Limit remaining entries, but not lower than waiting_count entries to
79      // prevent deadlock when command size is greater than the flush limit.
80      limit -= pending;
81      limit = limit < waiting_count ? waiting_count : limit;
82      immediate_entry_count_ =
83          immediate_entry_count_ > limit ? limit : immediate_entry_count_;
84    }
85  }
86}
87
88bool CommandBufferHelper::AllocateRingBuffer() {
89  if (!usable()) {
90    return false;
91  }
92
93  if (HaveRingBuffer()) {
94    return true;
95  }
96
97  int32 id = -1;
98  scoped_refptr<Buffer> buffer =
99      command_buffer_->CreateTransferBuffer(ring_buffer_size_, &id);
100  if (id < 0) {
101    ClearUsable();
102    return false;
103  }
104
105  ring_buffer_ = buffer;
106  ring_buffer_id_ = id;
107  command_buffer_->SetGetBuffer(id);
108  entries_ = static_cast<CommandBufferEntry*>(ring_buffer_->memory());
109  total_entry_count_ = ring_buffer_size_ / sizeof(CommandBufferEntry);
110  // Call to SetGetBuffer(id) above resets get and put offsets to 0.
111  // No need to query it through IPC.
112  put_ = 0;
113  CalcImmediateEntries(0);
114  return true;
115}
116
117void CommandBufferHelper::FreeResources() {
118  if (HaveRingBuffer()) {
119    command_buffer_->DestroyTransferBuffer(ring_buffer_id_);
120    ring_buffer_id_ = -1;
121    CalcImmediateEntries(0);
122  }
123}
124
125void CommandBufferHelper::FreeRingBuffer() {
126  CHECK((put_ == get_offset()) ||
127      error::IsError(command_buffer_->GetLastState().error));
128  FreeResources();
129}
130
131bool CommandBufferHelper::Initialize(int32 ring_buffer_size) {
132  ring_buffer_size_ = ring_buffer_size;
133  return AllocateRingBuffer();
134}
135
136CommandBufferHelper::~CommandBufferHelper() {
137  FreeResources();
138}
139
140bool CommandBufferHelper::WaitForGetOffsetInRange(int32 start, int32 end) {
141  if (!usable()) {
142    return false;
143  }
144  command_buffer_->WaitForGetOffsetInRange(start, end);
145  return command_buffer_->GetLastError() == gpu::error::kNoError;
146}
147
148void CommandBufferHelper::Flush() {
149  // Wrap put_ before flush.
150  if (put_ == total_entry_count_)
151    put_ = 0;
152
153  if (usable() && last_put_sent_ != put_) {
154    last_flush_time_ = base::TimeTicks::Now();
155    last_put_sent_ = put_;
156    command_buffer_->Flush(put_);
157    ++flush_generation_;
158    CalcImmediateEntries(0);
159  }
160}
161
162#if defined(CMD_HELPER_PERIODIC_FLUSH_CHECK)
163void CommandBufferHelper::PeriodicFlushCheck() {
164  base::TimeTicks current_time = base::TimeTicks::Now();
165  if (current_time - last_flush_time_ >
166      base::TimeDelta::FromMicroseconds(kPeriodicFlushDelayInMicroseconds)) {
167    Flush();
168  }
169}
170#endif
171
172// Calls Flush() and then waits until the buffer is empty. Break early if the
173// error is set.
174bool CommandBufferHelper::Finish() {
175  TRACE_EVENT0("gpu", "CommandBufferHelper::Finish");
176  if (!usable()) {
177    return false;
178  }
179  // If there is no work just exit.
180  if (put_ == get_offset()) {
181    return true;
182  }
183  DCHECK(HaveRingBuffer());
184  Flush();
185  if (!WaitForGetOffsetInRange(put_, put_))
186    return false;
187  DCHECK_EQ(get_offset(), put_);
188
189  CalcImmediateEntries(0);
190
191  return true;
192}
193
194// Inserts a new token into the command stream. It uses an increasing value
195// scheme so that we don't lose tokens (a token has passed if the current token
196// value is higher than that token). Calls Finish() if the token value wraps,
197// which will be rare.
198int32 CommandBufferHelper::InsertToken() {
199  AllocateRingBuffer();
200  if (!usable()) {
201    return token_;
202  }
203  DCHECK(HaveRingBuffer());
204  // Increment token as 31-bit integer. Negative values are used to signal an
205  // error.
206  token_ = (token_ + 1) & 0x7FFFFFFF;
207  cmd::SetToken* cmd = GetCmdSpace<cmd::SetToken>();
208  if (cmd) {
209    cmd->Init(token_);
210    if (token_ == 0) {
211      TRACE_EVENT0("gpu", "CommandBufferHelper::InsertToken(wrapped)");
212      // we wrapped
213      Finish();
214      DCHECK_EQ(token_, last_token_read());
215    }
216  }
217  return token_;
218}
219
220// Waits until the current token value is greater or equal to the value passed
221// in argument.
222void CommandBufferHelper::WaitForToken(int32 token) {
223  if (!usable() || !HaveRingBuffer()) {
224    return;
225  }
226  // Return immediately if corresponding InsertToken failed.
227  if (token < 0)
228    return;
229  if (token > token_) return;  // we wrapped
230  if (last_token_read() >= token)
231    return;
232  Flush();
233  command_buffer_->WaitForTokenInRange(token, token_);
234}
235
236// Waits for available entries, basically waiting until get >= put + count + 1.
237// It actually waits for contiguous entries, so it may need to wrap the buffer
238// around, adding a noops. Thus this function may change the value of put_. The
239// function will return early if an error occurs, in which case the available
240// space may not be available.
241void CommandBufferHelper::WaitForAvailableEntries(int32 count) {
242  AllocateRingBuffer();
243  if (!usable()) {
244    return;
245  }
246  DCHECK(HaveRingBuffer());
247  DCHECK(count < total_entry_count_);
248  if (put_ + count > total_entry_count_) {
249    // There's not enough room between the current put and the end of the
250    // buffer, so we need to wrap. We will add noops all the way to the end,
251    // but we need to make sure get wraps first, actually that get is 1 or
252    // more (since put will wrap to 0 after we add the noops).
253    DCHECK_LE(1, put_);
254    int32 curr_get = get_offset();
255    if (curr_get > put_ || curr_get == 0) {
256      TRACE_EVENT0("gpu", "CommandBufferHelper::WaitForAvailableEntries");
257      Flush();
258      if (!WaitForGetOffsetInRange(1, put_))
259        return;
260      curr_get = get_offset();
261      DCHECK_LE(curr_get, put_);
262      DCHECK_NE(0, curr_get);
263    }
264    // Insert Noops to fill out the buffer.
265    int32 num_entries = total_entry_count_ - put_;
266    while (num_entries > 0) {
267      int32 num_to_skip = std::min(CommandHeader::kMaxSize, num_entries);
268      cmd::Noop::Set(&entries_[put_], num_to_skip);
269      put_ += num_to_skip;
270      num_entries -= num_to_skip;
271    }
272    put_ = 0;
273  }
274
275  // Try to get 'count' entries without flushing.
276  CalcImmediateEntries(count);
277  if (immediate_entry_count_ < count) {
278    // Try again with a shallow Flush().
279    Flush();
280    CalcImmediateEntries(count);
281    if (immediate_entry_count_ < count) {
282      // Buffer is full.  Need to wait for entries.
283      TRACE_EVENT0("gpu", "CommandBufferHelper::WaitForAvailableEntries1");
284      if (!WaitForGetOffsetInRange(put_ + count + 1, put_))
285        return;
286      CalcImmediateEntries(count);
287      DCHECK_GE(immediate_entry_count_, count);
288    }
289  }
290}
291
292
293}  // namespace gpu
294