Mesa (master): mesa: don't count buffer references for the context that created them
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Sat Jan 30 22:15:46 UTC 2021
Module: Mesa
Branch: master
Commit: e014e3b6be638f4192d6eddd3d1033fd571f3a76
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=e014e3b6be638f4192d6eddd3d1033fd571f3a76
Author: Marek Olšák <marek.olsak at amd.com>
Date: Mon Jan 4 15:25:18 2021 -0500
mesa: don't count buffer references for the context that created them
See mtypes.h - it gives you the top level view of how it works, and other
code contains a lot of comments.
Reviewed-by: Zoltán Böszörményi <zboszor at gmail.com>
Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8606>
---
src/mesa/main/bufferobj.c | 200 ++++++++++++++++++++++++++++++++++++++++++++--
src/mesa/main/bufferobj.h | 22 ++++-
src/mesa/main/context.c | 6 +-
src/mesa/main/mtypes.h | 41 ++++++++++
src/mesa/main/shared.c | 9 +++
src/mesa/main/teximage.c | 2 +-
src/mesa/main/texobj.c | 2 +-
7 files changed, 272 insertions(+), 10 deletions(-)
diff --git a/src/mesa/main/bufferobj.c b/src/mesa/main/bufferobj.c
index 738af3bd93b..c9ca8bbcf72 100644
--- a/src/mesa/main/bufferobj.c
+++ b/src/mesa/main/bufferobj.c
@@ -47,6 +47,7 @@
#include "varray.h"
#include "util/u_atomic.h"
#include "util/u_memory.h"
+#include "util/set.h"
/* Debug flags */
@@ -506,13 +507,19 @@ _mesa_delete_buffer_object(struct gl_context *ctx,
void
_mesa_reference_buffer_object_(struct gl_context *ctx,
struct gl_buffer_object **ptr,
- struct gl_buffer_object *bufObj)
+ struct gl_buffer_object *bufObj,
+ bool shared_binding)
{
if (*ptr) {
/* Unreference the old buffer */
struct gl_buffer_object *oldObj = *ptr;
- if (p_atomic_dec_zero(&oldObj->RefCount)) {
+ /* Count references only if the context doesn't own the buffer or if
+ * ptr is a binding point shared by multiple contexts (such as a texture
+ * buffer object being a buffer bound within a texture object).
+ */
+ if ((shared_binding || ctx != oldObj->Ctx) &&
+ p_atomic_dec_zero(&oldObj->RefCount)) {
assert(ctx->Driver.DeleteBuffer);
ctx->Driver.DeleteBuffer(ctx, oldObj);
}
@@ -523,7 +530,8 @@ _mesa_reference_buffer_object_(struct gl_context *ctx,
if (bufObj) {
/* reference new buffer */
- p_atomic_inc(&bufObj->RefCount);
+ if (shared_binding || ctx != bufObj->Ctx)
+ p_atomic_inc(&bufObj->RefCount);
*ptr = bufObj;
}
}
@@ -903,6 +911,59 @@ _mesa_init_buffer_objects( struct gl_context *ctx )
}
}
+/**
+ * Zombie buffers are buffers that were created by one context and deleted
+ * by another context. The creating context holds a global reference for each
+ * buffer it created that can't be unreferenced when another context deletes
+ * it. Such a buffer becomes a zombie, which means that it's no longer usable
+ * by OpenGL, but the creating context still holds its global reference of
+ * the buffer. Only the creating context can remove the reference, which is
+ * what this function does.
+ *
+ * For all zombie buffers, decrement the reference count if the current
+ * context owns the buffer.
+ */
+static void
+unreference_zombie_buffers_for_ctx(struct gl_context *ctx)
+{
+ /* It's assumed that the mutex of Shared->BufferObjects is locked. */
+ set_foreach(ctx->Shared->ZombieBufferObjects, entry) {
+ struct gl_buffer_object *buf = (struct gl_buffer_object *)entry->key;
+
+ if (buf->Ctx == ctx) {
+ _mesa_set_remove(ctx->Shared->ZombieBufferObjects, entry);
+ buf->Ctx = NULL;
+ _mesa_reference_buffer_object(ctx, &buf, NULL);
+ }
+ }
+}
+
+/**
+ * When a context creates buffers, it holds a global buffer reference count
+ * for each buffer and doesn't update their RefCount. When the context is
+ * destroyed before the buffers are destroyed, the context must remove
+ * its global reference from the buffers, so that the buffers can live
+ * on their own.
+ *
+ * At this point, the buffers shouldn't be bound in any bounding point owned
+ * by the context. (it would crash if they did)
+ */
+static void
+detach_unrefcounted_buffer_from_ctx(void *data, void *userData)
+{
+ struct gl_context *ctx = (struct gl_context *)userData;
+ struct gl_buffer_object *buf = (struct gl_buffer_object *)data;
+
+ if (buf->Ctx == ctx) {
+ /* Detach the current context from live objects. There should be no
+ * bound buffer in the context at this point, therefore we can just
+ * unreference the global reference. Other contexts and texture objects
+ * might still be using the buffer.
+ */
+ buf->Ctx = NULL;
+ _mesa_reference_buffer_object(ctx, &buf, NULL);
+ }
+}
void
_mesa_free_buffer_objects( struct gl_context *ctx )
@@ -946,6 +1007,28 @@ _mesa_free_buffer_objects( struct gl_context *ctx )
NULL);
}
+ _mesa_HashLockMutex(ctx->Shared->BufferObjects);
+ unreference_zombie_buffers_for_ctx(ctx);
+ _mesa_HashWalkLocked(ctx->Shared->BufferObjects,
+ detach_unrefcounted_buffer_from_ctx, ctx);
+ _mesa_HashUnlockMutex(ctx->Shared->BufferObjects);
+}
+
+/**
+ * Create a buffer object that will be backed by an OpenGL buffer ID
+ * where the creating context will hold one global buffer reference instead
+ * of updating buffer RefCount for every binding point.
+ *
+ * This shouldn't be used for internal buffers.
+ */
+static struct gl_buffer_object *
+new_gl_buffer_object(struct gl_context *ctx, GLuint id)
+{
+ struct gl_buffer_object *buf = ctx->Driver.NewBufferObject(ctx, id);
+
+ buf->Ctx = ctx;
+ buf->RefCount++; /* global buffer reference held by the context */
+ return buf;
}
bool
@@ -965,7 +1048,7 @@ _mesa_handle_bind_buffer_gen(struct gl_context *ctx,
/* If this is a new buffer object id, or one which was generated but
* never used before, allocate a buffer object now.
*/
- *buf_handle = ctx->Driver.NewBufferObject(ctx, buffer);
+ *buf_handle = new_gl_buffer_object(ctx, buffer);
if (!*buf_handle) {
_mesa_error(ctx, GL_OUT_OF_MEMORY, "%s", caller);
return false;
@@ -1447,6 +1530,82 @@ bind_buffer_base_atomic_buffer(struct gl_context *ctx,
bind_atomic_buffer(ctx, index, bufObj, 0, 0, GL_TRUE);
}
+struct hash_walk_input {
+ struct gl_context *ctx;
+ struct gl_buffer_object *buf;
+};
+
+/**
+ * When a buffer ID is deleted, the buffer is unbound from the current VAO
+ * but stays bound in other VAOs until they are deleted too.
+ * When the context owns the buffer reference globally, it doesn't count
+ * buffer references for the context. When the buffer is deleted, the context
+ * gives up its ownership, and thus it has to increase the buffer reference
+ * count for each binding point where the buffer is bound.
+ */
+static void
+detach_ctx_from_vao_buffers(void *data, void *user)
+{
+ struct gl_context *ctx = ((struct hash_walk_input *)user)->ctx;
+ struct gl_buffer_object *buf = ((struct hash_walk_input *)user)->buf;
+ struct gl_vertex_array_object *vao = (struct gl_vertex_array_object *)data;
+
+ /* The buffer should already be unbound in the currently-bound VAO. */
+ if (vao == ctx->Array.VAO)
+ return;
+
+ /* Increase the reference count for each binding point where the buffer is
+ * bound.
+ */
+ unsigned add_count = 0;
+
+ if (vao->IndexBufferObj == buf)
+ add_count++;
+
+ for (unsigned i = 0; i < ARRAY_SIZE(vao->BufferBinding); i++) {
+ if (vao->BufferBinding[i].BufferObj == buf)
+ add_count++;
+ }
+
+ if (add_count)
+ p_atomic_add(&buf->RefCount, add_count);
+}
+
+/**
+ * When a buffer ID is deleted, the buffer is unbound from the current
+ * transform feedback object but stays bound in other TFBs until they are
+ * deleted too.
+ *
+ * When the context owns the buffer reference globally, it doesn't count
+ * buffer references for the context. When the buffer is deleted, the context
+ * gives up its ownership, and thus it has to increase the buffer reference
+ * count for each binding point where the buffer is bound.
+ */
+static void
+detach_ctx_from_tfb_buffers(void *data, void *user)
+{
+ struct gl_context *ctx = ((struct hash_walk_input *)user)->ctx;
+ struct gl_buffer_object *buf = ((struct hash_walk_input *)user)->buf;
+ struct gl_transform_feedback_object *tfb =
+ (struct gl_transform_feedback_object *)data;
+
+ /* The buffer should already be unbound in the currently-bound TFB. */
+ if (tfb == ctx->TransformFeedback.CurrentObject)
+ return;
+
+ /* Increase the reference count for each binding point where the buffer is
+ * bound.
+ */
+ unsigned add_count = 0;
+ for (unsigned i = 0; i < ARRAY_SIZE(tfb->Buffers); i++) {
+ if (tfb->Buffers[i] == buf)
+ add_count++;
+ }
+
+ if (add_count)
+ p_atomic_add(&buf->RefCount, add_count);
+}
+
/**
* Delete a set of buffer objects.
*
@@ -1460,6 +1619,7 @@ delete_buffers(struct gl_context *ctx, GLsizei n, const GLuint *ids)
_mesa_HashLockMaybeLocked(ctx->Shared->BufferObjects,
ctx->BufferObjectsLocked);
+ unreference_zombie_buffers_for_ctx(ctx);
for (GLsizei i = 0; i < n; i++) {
struct gl_buffer_object *bufObj =
@@ -1586,6 +1746,36 @@ delete_buffers(struct gl_context *ctx, GLsizei n, const GLuint *ids)
* which would introduce more runtime overhead than this.
*/
bufObj->DeletePending = GL_TRUE;
+
+ if (bufObj->Ctx == ctx) {
+ struct hash_walk_input input = {ctx, bufObj};
+
+ /* Increase reference counts for all binding points where
+ * the buffer remains bound after deleting. This is needed to
+ * enable reference counting for the buffer for this context
+ * because the context only holds the global buffer reference
+ * while the GL buffer ID exists.
+ */
+ _mesa_HashWalk(ctx->Array.Objects,
+ detach_ctx_from_vao_buffers, &input);
+ detach_ctx_from_vao_buffers(ctx->Array.DefaultVAO, &input);
+
+ _mesa_HashWalk(ctx->TransformFeedback.Objects,
+ detach_ctx_from_tfb_buffers, &input);
+ detach_ctx_from_tfb_buffers(ctx->TransformFeedback.DefaultObject,
+ &input);
+
+ /* Remove the context reference where the context holds one
+ * reference for the lifetime of the buffer ID to skip refcount
+ * atomics instead of each binding point holding the reference.
+ */
+ p_atomic_dec(&bufObj->RefCount);
+ bufObj->Ctx = NULL;
+ } else if (bufObj->Ctx) {
+ /* Only the context holding it can release it. */
+ _mesa_set_add(ctx->Shared->ZombieBufferObjects, bufObj);
+ }
+
_mesa_reference_buffer_object(ctx, &bufObj, NULL);
}
}
@@ -1645,7 +1835,7 @@ create_buffers(struct gl_context *ctx, GLsizei n, GLuint *buffers, bool dsa)
for (int i = 0; i < n; i++) {
if (dsa) {
assert(ctx->Driver.NewBufferObject);
- buf = ctx->Driver.NewBufferObject(ctx, buffers[i]);
+ buf = new_gl_buffer_object(ctx, buffers[i]);
if (!buf) {
_mesa_error(ctx, GL_OUT_OF_MEMORY, "glCreateBuffers");
_mesa_HashUnlockMaybeLocked(ctx->Shared->BufferObjects,
diff --git a/src/mesa/main/bufferobj.h b/src/mesa/main/bufferobj.h
index bcafd350e70..198bf74a02b 100644
--- a/src/mesa/main/bufferobj.h
+++ b/src/mesa/main/bufferobj.h
@@ -105,15 +105,33 @@ _mesa_delete_buffer_object(struct gl_context *ctx,
extern void
_mesa_reference_buffer_object_(struct gl_context *ctx,
struct gl_buffer_object **ptr,
- struct gl_buffer_object *bufObj);
+ struct gl_buffer_object *bufObj,
+ bool shared_binding);
+/**
+ * Assign a buffer into a pointer with reference counting. The destination
+ * must be private within a context.
+ */
static inline void
_mesa_reference_buffer_object(struct gl_context *ctx,
struct gl_buffer_object **ptr,
struct gl_buffer_object *bufObj)
{
if (*ptr != bufObj)
- _mesa_reference_buffer_object_(ctx, ptr, bufObj);
+ _mesa_reference_buffer_object_(ctx, ptr, bufObj, false);
+}
+
+/**
+ * Assign a buffer into a pointer with reference counting. The destination
+ * must be shareable among multiple contexts.
+ */
+static inline void
+_mesa_reference_buffer_object_shared(struct gl_context *ctx,
+ struct gl_buffer_object **ptr,
+ struct gl_buffer_object *bufObj)
+{
+ if (*ptr != bufObj)
+ _mesa_reference_buffer_object_(ctx, ptr, bufObj, true);
}
extern GLuint
diff --git a/src/mesa/main/context.c b/src/mesa/main/context.c
index 31ddef85708..8442d0b5f12 100644
--- a/src/mesa/main/context.c
+++ b/src/mesa/main/context.c
@@ -1346,7 +1346,6 @@ _mesa_free_context_data(struct gl_context *ctx, bool destroy_debug_output)
_mesa_reference_vao(ctx, &ctx->Array._DrawVAO, NULL);
_mesa_free_attrib_data(ctx);
- _mesa_free_buffer_objects(ctx);
_mesa_free_eval_data( ctx );
_mesa_free_texture_data( ctx );
_mesa_free_image_textures(ctx);
@@ -1367,6 +1366,11 @@ _mesa_free_context_data(struct gl_context *ctx, bool destroy_debug_output)
_mesa_reference_buffer_object(ctx, &ctx->DefaultPacking.BufferObj, NULL);
_mesa_reference_buffer_object(ctx, &ctx->Array.ArrayBufferObj, NULL);
+ /* This must be called after all buffers are unbound because global buffer
+ * references that this context holds will be removed.
+ */
+ _mesa_free_buffer_objects(ctx);
+
/* free dispatch tables */
free(ctx->BeginEnd);
free(ctx->OutsideBeginEnd);
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 2c7bdf4fa66..e862649fcdf 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -1402,6 +1402,34 @@ struct gl_buffer_object
GLint RefCount;
GLuint Name;
GLchar *Label; /**< GL_KHR_debug */
+
+ /**
+ * The context that holds a global buffer reference for the lifetime of
+ * the GL buffer ID to skip refcounting for all its private bind points.
+ * Other contexts must still do refcounting as usual. Shared binding points
+ * like TBO within gl_texture_object are always refcounted.
+ *
+ * Implementation details:
+ * - Only the context that creates the buffer ("creating context") skips
+ * refcounting.
+ * - Only buffers represented by an OpenGL buffer ID skip refcounting.
+ * Other internal buffers don't. (glthread requires refcounting for
+ * internal buffers, etc.)
+ * - glDeleteBuffers removes the global buffer reference and increments
+ * RefCount for all private bind points where the deleted buffer is bound
+ * (e.g. unbound VAOs that are not changed by glDeleteBuffers),
+ * effectively enabling refcounting for that context. This is the main
+ * point where the global buffer reference is removed.
+ * - glDeleteBuffers called from a different context adds the buffer into
+ * the ZombieBufferObjects list, which is a way to notify the creating
+ * context that it should remove its global buffer reference to allow
+ * freeing the buffer. The creating context walks over that list in a few
+ * GL functions.
+ * - xxxDestroyContext walks over all buffers and removes its global
+ * reference from those buffers that it created.
+ */
+ struct gl_context *Ctx;
+
GLenum16 Usage; /**< GL_STREAM_DRAW_ARB, GL_STREAM_READ_ARB, etc. */
GLbitfield StorageFlags; /**< GL_MAP_PERSISTENT_BIT, etc. */
GLsizeiptrARB Size; /**< Size of buffer storage in bytes */
@@ -3401,6 +3429,19 @@ struct gl_shared_state
struct _mesa_HashTable *BufferObjects;
+ /* Buffer objects released by a different context than the one that
+ * created them. Since the creating context holds one global buffer
+ * reference for each buffer it created and skips reference counting,
+ * deleting a buffer by another context can't touch the buffer reference
+ * held by the context that created it. Only the creating context can
+ * remove its global buffer reference.
+ *
+ * This list contains all buffers that were deleted by a different context
+ * than the one that created them. This list should be probed by all
+ * contexts regularly and remove references of those buffers that they own.
+ */
+ struct set *ZombieBufferObjects;
+
/** Table of both gl_shader and gl_shader_program objects */
struct _mesa_HashTable *ShaderObjects;
diff --git a/src/mesa/main/shared.c b/src/mesa/main/shared.c
index b4f92065652..1a5353479b8 100644
--- a/src/mesa/main/shared.c
+++ b/src/mesa/main/shared.c
@@ -85,6 +85,8 @@ _mesa_alloc_shared_state(struct gl_context *ctx)
shared->ShaderObjects = _mesa_NewHashTable();
shared->BufferObjects = _mesa_NewHashTable();
+ shared->ZombieBufferObjects = _mesa_set_create(NULL, _mesa_hash_pointer,
+ _mesa_key_pointer_equal);
/* GL_ARB_sampler_objects */
shared->SamplerObjects = _mesa_NewHashTable();
@@ -391,6 +393,13 @@ free_shared_state(struct gl_context *ctx, struct gl_shared_state *shared)
_mesa_DeleteHashTable(shared->BufferObjects);
}
+ if (shared->ZombieBufferObjects) {
+ set_foreach(shared->ZombieBufferObjects, entry) {
+ assert(!"ZombieBufferObjects should be empty");
+ }
+ _mesa_set_destroy(shared->ZombieBufferObjects, NULL);
+ }
+
if (shared->FrameBuffers) {
_mesa_HashDeleteAll(shared->FrameBuffers, delete_framebuffer_cb, ctx);
_mesa_DeleteHashTable(shared->FrameBuffers);
diff --git a/src/mesa/main/teximage.c b/src/mesa/main/teximage.c
index f431136aef4..f6eb1b37631 100644
--- a/src/mesa/main/teximage.c
+++ b/src/mesa/main/teximage.c
@@ -6335,7 +6335,7 @@ texture_buffer_range(struct gl_context *ctx,
_mesa_lock_texture(ctx, texObj);
{
- _mesa_reference_buffer_object(ctx, &texObj->BufferObject, bufObj);
+ _mesa_reference_buffer_object_shared(ctx, &texObj->BufferObject, bufObj);
texObj->BufferObjectFormat = internalFormat;
texObj->_BufferObjectFormat = format;
texObj->BufferOffset = offset;
diff --git a/src/mesa/main/texobj.c b/src/mesa/main/texobj.c
index 3fc232bf214..137ffaa3c77 100644
--- a/src/mesa/main/texobj.c
+++ b/src/mesa/main/texobj.c
@@ -447,7 +447,7 @@ _mesa_delete_texture_object(struct gl_context *ctx,
/* Delete all texture/image handles. */
_mesa_delete_texture_handles(ctx, texObj);
- _mesa_reference_buffer_object(ctx, &texObj->BufferObject, NULL);
+ _mesa_reference_buffer_object_shared(ctx, &texObj->BufferObject, NULL);
/* destroy the mutex -- it may have allocated memory (eg on bsd) */
simple_mtx_destroy(&texObj->Mutex);
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