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
  40 #ifdef HAVE_PTHREAD
  41
  42 static void
  43 glthread_allocate_batch(struct gl_context *ctx)
  44 {
  45    struct glthread_state *glthread = ctx->GLThread;
  46
  47    /* TODO: handle memory allocation failure. */
  48    glthread->batch = calloc(1, sizeof(*glthread->batch));
  49    if (!glthread->batch)
  50       return;
  51    glthread->batch->buffer = malloc(MARSHAL_MAX_CMD_SIZE);
  52 }
  53
  54 static void
  55 glthread_unmarshal_batch(struct gl_context *ctx, struct glthread_batch *batch)
  56 {
  57    size_t pos = 0;
  58
  59    _glapi_set_dispatch(ctx->CurrentServerDispatch);
  60
  61    while (pos < batch->used)
  62       pos += _mesa_unmarshal_dispatch_cmd(ctx, &batch->buffer[pos]);
  63
  64    assert(pos == batch->used);
  65
  66    free(batch->buffer);
  67    free(batch);
  68 }
  69
  70 static void *
  71 glthread_worker(void *data)
  72 {
  73    struct gl_context *ctx = data;
  74    struct glthread_state *glthread = ctx->GLThread;
  75
  76    ctx->Driver.SetBackgroundContext(ctx);
  77    _glapi_set_context(ctx);
  78
  79    pthread_mutex_lock(&glthread->mutex);
  80
  81    while (true) {
  82       struct glthread_batch *batch;
  83
  84       /* Block (dropping the lock) until new work arrives for us. */
  85       while (!glthread->batch_queue && !glthread->shutdown) {
  86          pthread_cond_broadcast(&glthread->work_done);
  87          pthread_cond_wait(&glthread->new_work, &glthread->mutex);
  88       }
  89
  90       batch = glthread->batch_queue;
  91
  92       if (glthread->shutdown && !batch) {
  93          pthread_cond_broadcast(&glthread->work_done);
  94          pthread_mutex_unlock(&glthread->mutex);
  95          return NULL;
  96       }
  97       glthread->batch_queue = batch->next;
  98       if (glthread->batch_queue_tail == &batch->next)
  99          glthread->batch_queue_tail = &glthread->batch_queue;
 100
 101       glthread->busy = true;
 102       pthread_mutex_unlock(&glthread->mutex);
 103
 104       glthread_unmarshal_batch(ctx, batch);
 105
 106       pthread_mutex_lock(&glthread->mutex);
 107       glthread->busy = false;
 108    }
 109
 110    /* UNREACHED */
 111    return NULL;
 112 }
 113
 114 void
 115 _mesa_glthread_init(struct gl_context *ctx)
 116 {
 117    struct glthread_state *glthread = calloc(1, sizeof(*glthread));
 118
 119    if (!glthread)
 120       return;
 121
 122    ctx->MarshalExec = _mesa_create_marshal_table(ctx);
 123    if (!ctx->MarshalExec) {
 124       free(glthread);
 125       return;
 126    }
 127
 128    ctx->CurrentClientDispatch = ctx->MarshalExec;
 129
 130    pthread_mutex_init(&glthread->mutex, NULL);
 131    pthread_cond_init(&glthread->new_work, NULL);
 132    pthread_cond_init(&glthread->work_done, NULL);
 133
 134    glthread->batch_queue_tail = &glthread->batch_queue;
 135    ctx->GLThread = glthread;
 136
 137    glthread_allocate_batch(ctx);
 138
 139    pthread_create(&glthread->thread, NULL, glthread_worker, ctx);
 140 }
 141
 142 void
 143 _mesa_glthread_destroy(struct gl_context *ctx)
 144 {
 145    struct glthread_state *glthread = ctx->GLThread;
 146
 147    if (!glthread)
 148       return;
 149
 150    _mesa_glthread_flush_batch(ctx);
 151
 152    pthread_mutex_lock(&glthread->mutex);
 153    glthread->shutdown = true;
 154    pthread_cond_broadcast(&glthread->new_work);
 155    pthread_mutex_unlock(&glthread->mutex);
 156
 157    /* Since this waits for the thread to exit, it means that all queued work
 158     * will have been completed.
 159     */
 160    pthread_join(glthread->thread, NULL);
 161
 162    pthread_cond_destroy(&glthread->new_work);
 163    pthread_cond_destroy(&glthread->work_done);
 164    pthread_mutex_destroy(&glthread->mutex);
 165
 166    /* Due to the join above, there should be one empty batch allocated at this
 167     * point, and no batches queued.
 168     */
 169    assert(!glthread->batch->used);
 170    assert(!glthread->batch->next);
 171    free(glthread->batch);
 172    assert(!glthread->batch_queue);
 173
 174    free(glthread);
 175    ctx->GLThread = NULL;
 176
 177    /* Remove ourselves from the dispatch table. */
 178    ctx->CurrentClientDispatch = ctx->CurrentServerDispatch;
 179    _glapi_set_dispatch(ctx->CurrentClientDispatch);
 180 }
 181
 182 void
 183 _mesa_glthread_flush_batch(struct gl_context *ctx)
 184 {
 185    struct glthread_state *glthread = ctx->GLThread;
 186    struct glthread_batch *batch;
 187
 188    if (!glthread)
 189       return;
 190
 191    batch = glthread->batch;
 192    if (!batch->used)
 193       return;
 194
 195    /* Immediately reallocate a new batch, since the next marshalled call would
 196     * just do it.
 197     */
 198    glthread_allocate_batch(ctx);
 199
 200    /* Debug: execute the batch immediately from this thread.
 201     *
 202     * Note that glthread_unmarshal_batch() changes the dispatch table so we'll
 203     * need to restore it when it returns.
 204     */
 205    if (false) {
 206       glthread_unmarshal_batch(ctx, batch);
 207       _glapi_set_dispatch(ctx->CurrentClientDispatch);
 208       return;
 209    }
 210
 211    pthread_mutex_lock(&glthread->mutex);
 212    *glthread->batch_queue_tail = batch;
 213    glthread->batch_queue_tail = &batch->next;
 214    pthread_cond_broadcast(&glthread->new_work);
 215    pthread_mutex_unlock(&glthread->mutex);
 216 }
 217
 218 /**
 219  * Waits for all pending batches have been unmarshaled.
 220  *
 221  * This can be used by the main thread to synchronize access to the context,
 222  * since the worker thread will be idle after this.
 223  */
 224 void
 225 _mesa_glthread_finish(struct gl_context *ctx)
 226 {
 227    struct glthread_state *glthread = ctx->GLThread;
 228
 229    if (!glthread)
 230       return;
 231
 232    /* If this is called from the worker thread, then we've hit a path that
 233     * might be called from either the main thread or the worker (such as some
 234     * dri interface entrypoints), in which case we don't need to actually
 235     * synchronize against ourself.
 236     */
 237    if (pthread_self() == glthread->thread)
 238       return;
 239
 240    _mesa_glthread_flush_batch(ctx);
 241
 242    pthread_mutex_lock(&glthread->mutex);
 243
 244    while (glthread->batch_queue || glthread->busy)
 245       pthread_cond_wait(&glthread->work_done, &glthread->mutex);
 246
 247    pthread_mutex_unlock(&glthread->mutex);
 248 }
 249
 250 #endif