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