src/mesa/main/glthread.c

   1 /*
   2  * Copyright © 2012 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 /** @file glthread.c
  25  *
  26  * Support functions for the glthread feature of Mesa.
  27  *
  28  * In multicore systems, many applications end up CPU-bound with about half
  29  * their time spent inside their rendering thread and half inside Mesa.  To
  30  * alleviate this, we put a shim layer in Mesa at the GL dispatch level that
  31  * quickly logs the GL commands to a buffer to be processed by a worker
  32  * thread.
  33  */
  34
  35 #include "main/mtypes.h"
  36 #include "main/glthread.h"
  37 #include "main/marshal.h"
  38 #include "main/marshal_generated.h"
  39 #include "util/u_thread.h"
  40
  41 #ifdef HAVE_PTHREAD
  42
  43 static void
  44 glthread_allocate_batch(struct gl_context *ctx)
  45 {
  46    struct glthread_state *glthread = ctx->GLThread;
  47
  48    /* TODO: handle memory allocation failure. */
  49    glthread->batch = malloc(sizeof(*glthread->batch));
  50    if (!glthread->batch)
  51       return;
  52    memset(glthread->batch, 0, offsetof(struct glthread_batch, buffer));
  53 }
  54
  55 static void
  56 glthread_unmarshal_batch(struct gl_context *ctx, struct glthread_batch *batch,
  57                          const bool release_batch)
  58 {
  59    size_t pos = 0;
  60
  61    _glapi_set_dispatch(ctx->CurrentServerDispatch);
  62
  63    while (pos < batch->used)
  64       pos += _mesa_unmarshal_dispatch_cmd(ctx, &batch->buffer[pos]);
  65
  66    assert(pos == batch->used);
  67
  68    if (release_batch)
  69       free(batch);
  70    else
  71       batch->used = 0;
  72 }
  73
  74 static void *
  75 glthread_worker(void *data)
  76 {
  77    struct gl_context *ctx = data;
  78    struct glthread_state *glthread = ctx->GLThread;
  79
  80    ctx->Driver.SetBackgroundContext(ctx);
  81    _glapi_set_context(ctx);
  82
  83    u_thread_setname("mesa_glthread");
  84
  85    pthread_mutex_lock(&glthread->mutex);
  86
  87    while (true) {
  88       struct glthread_batch *batch;
  89
  90       /* Block (dropping the lock) until new work arrives for us. */
  91       while (!glthread->batch_queue && !glthread->shutdown) {
  92          pthread_cond_broadcast(&glthread->work_done);
  93          pthread_cond_wait(&glthread->new_work, &glthread->mutex);
  94       }
  95
  96       batch = glthread->batch_queue;
  97
  98       if (glthread->shutdown && !batch) {
  99          pthread_cond_broadcast(&glthread->work_done);
 100          pthread_mutex_unlock(&glthread->mutex);
 101          return NULL;
 102       }
 103       glthread->batch_queue = batch->next;
 104       if (glthread->batch_queue_tail == &batch->next)
 105          glthread->batch_queue_tail = &glthread->batch_queue;
 106
 107       glthread->busy = true;
 108       pthread_mutex_unlock(&glthread->mutex);
 109
 110       glthread_unmarshal_batch(ctx, batch, true);
 111
 112       pthread_mutex_lock(&glthread->mutex);
 113       glthread->busy = false;
 114    }
 115
 116    /* UNREACHED */
 117    return NULL;
 118 }
 119
 120 void
 121 _mesa_glthread_init(struct gl_context *ctx)
 122 {
 123    struct glthread_state *glthread = calloc(1, sizeof(*glthread));
 124
 125    if (!glthread)
 126       return;
 127
 128    ctx->MarshalExec = _mesa_create_marshal_table(ctx);
 129    if (!ctx->MarshalExec) {
 130       free(glthread);
 131       return;
 132    }
 133
 134    ctx->CurrentClientDispatch = ctx->MarshalExec;
 135
 136    pthread_mutex_init(&glthread->mutex, NULL);
 137    pthread_cond_init(&glthread->new_work, NULL);
 138    pthread_cond_init(&glthread->work_done, NULL);
 139
 140    glthread->batch_queue_tail = &glthread->batch_queue;
 141    ctx->GLThread = glthread;
 142
 143    glthread_allocate_batch(ctx);
 144
 145    pthread_create(&glthread->thread, NULL, glthread_worker, ctx);
 146 }
 147
 148 void
 149 _mesa_glthread_destroy(struct gl_context *ctx)
 150 {
 151    struct glthread_state *glthread = ctx->GLThread;
 152
 153    if (!glthread)
 154       return;
 155
 156    _mesa_glthread_flush_batch(ctx);
 157
 158    pthread_mutex_lock(&glthread->mutex);
 159    glthread->shutdown = true;
 160    pthread_cond_broadcast(&glthread->new_work);
 161    pthread_mutex_unlock(&glthread->mutex);
 162
 163    /* Since this waits for the thread to exit, it means that all queued work
 164     * will have been completed.
 165     */
 166    pthread_join(glthread->thread, NULL);
 167
 168    pthread_cond_destroy(&glthread->new_work);
 169    pthread_cond_destroy(&glthread->work_done);
 170    pthread_mutex_destroy(&glthread->mutex);
 171
 172    /* Due to the join above, there should be one empty batch allocated at this
 173     * point, and no batches queued.
 174     */
 175    assert(!glthread->batch->used);
 176    assert(!glthread->batch->next);
 177    free(glthread->batch);
 178    assert(!glthread->batch_queue);
 179
 180    free(glthread);
 181    ctx->GLThread = NULL;
 182
 183    _mesa_glthread_restore_dispatch(ctx);
 184 }
 185
 186 void
 187 _mesa_glthread_restore_dispatch(struct gl_context *ctx)
 188 {
 189    /* Remove ourselves from the dispatch table except if another ctx/thread
 190     * already installed a new dispatch table.
 191     *
 192     * Typically glxMakeCurrent will bind a new context (install new table) then
 193     * old context might be deleted.
 194     */
 195    if (_glapi_get_dispatch() == ctx->MarshalExec) {
 196        ctx->CurrentClientDispatch = ctx->CurrentServerDispatch;
 197        _glapi_set_dispatch(ctx->CurrentClientDispatch);
 198    }
 199 }
 200
 201 static void
 202 _mesa_glthread_flush_batch_locked(struct gl_context *ctx)
 203 {
 204    struct glthread_state *glthread = ctx->GLThread;
 205    struct glthread_batch *batch = glthread->batch;
 206
 207    if (!batch->used)
 208       return;
 209
 210    /* Immediately reallocate a new batch, since the next marshalled call would
 211     * just do it.
 212     */
 213    glthread_allocate_batch(ctx);
 214
 215    /* Debug: execute the batch immediately from this thread.
 216     *
 217     * Note that glthread_unmarshal_batch() changes the dispatch table so we'll
 218     * need to restore it when it returns.
 219     */
 220    if (false) {
 221       glthread_unmarshal_batch(ctx, batch, true);
 222       _glapi_set_dispatch(ctx->CurrentClientDispatch);
 223       return;
 224    }
 225
 226    *glthread->batch_queue_tail = batch;
 227    glthread->batch_queue_tail = &batch->next;
 228    pthread_cond_broadcast(&glthread->new_work);
 229 }
 230
 231 void
 232 _mesa_glthread_flush_batch(struct gl_context *ctx)
 233 {
 234    struct glthread_state *glthread = ctx->GLThread;
 235    struct glthread_batch *batch;
 236
 237    if (!glthread)
 238       return;
 239
 240    batch = glthread->batch;
 241    if (!batch->used)
 242       return;
 243
 244    pthread_mutex_lock(&glthread->mutex);
 245    _mesa_glthread_flush_batch_locked(ctx);
 246    pthread_mutex_unlock(&glthread->mutex);
 247 }
 248
 249 /**
 250  * Waits for all pending batches have been unmarshaled.
 251  *
 252  * This can be used by the main thread to synchronize access to the context,
 253  * since the worker thread will be idle after this.
 254  */
 255 void
 256 _mesa_glthread_finish(struct gl_context *ctx)
 257 {
 258    struct glthread_state *glthread = ctx->GLThread;
 259
 260    if (!glthread)
 261       return;
 262
 263    /* If this is called from the worker thread, then we've hit a path that
 264     * might be called from either the main thread or the worker (such as some
 265     * dri interface entrypoints), in which case we don't need to actually
 266     * synchronize against ourself.
 267     */
 268    if (pthread_self() == glthread->thread)
 269       return;
 270
 271    pthread_mutex_lock(&glthread->mutex);
 272
 273    if (!(glthread->batch_queue || glthread->busy)) {
 274       if (glthread->batch && glthread->batch->used) {
 275          struct _glapi_table *dispatch = _glapi_get_dispatch();
 276          glthread_unmarshal_batch(ctx, glthread->batch, false);
 277          _glapi_set_dispatch(dispatch);
 278       }
 279    } else {
 280       _mesa_glthread_flush_batch_locked(ctx);
 281       while (glthread->batch_queue || glthread->busy)
 282          pthread_cond_wait(&glthread->work_done, &glthread->mutex);
 283    }
 284
 285    pthread_mutex_unlock(&glthread->mutex);
 286 }
 287
 288 #endif