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dmabuf: share the mapping with shared copies of the memory

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With lots of shared memory instances (e.g. created by a RTP payloader) the
overhead of duplicating the file descriptor and creating extra mappings is
significant. To avoid this, the parent memory maps the whole region and the
shared copies just reuse the same mapping.

https://bugzilla.gnome.org/show_bug.cgi?id=730441
This commit is contained in:
Michael Olbrich 2014-05-20 11:18:56 +02:00 committed by Nicolas Dufresne
parent d8a1dc5ea8
commit b60888fd4b
1 changed files with 14 additions and 9 deletions
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23
gst-libs/gst/allocators/gstdmabuf.c
View file

@ -53,7 +53,6 @@ typedef struct
gpointer data; gpointer data;
gint mmapping_flags; gint mmapping_flags;
gint mmap_count; gint mmap_count;
gsize mmap_size;
GMutex lock; GMutex lock;
} GstDmaBufMemory; } GstDmaBufMemory;
@ -68,9 +67,10 @@ gst_dmabuf_allocator_free (GstAllocator * allocator, GstMemory * gmem)
if (mem->data) { if (mem->data) {
g_warning (G_STRLOC ":%s: Freeing memory %p still mapped", G_STRFUNC, mem); g_warning (G_STRLOC ":%s: Freeing memory %p still mapped", G_STRFUNC, mem);
munmap ((void *) mem->data, mem->mmap_size); munmap ((void *) mem->data, gmem->maxsize);
} }
close (mem->fd); if (mem->fd >= 0)
close (mem->fd);
g_mutex_clear (&mem->lock); g_mutex_clear (&mem->lock);
g_slice_free (GstDmaBufMemory, mem); g_slice_free (GstDmaBufMemory, mem);
GST_DEBUG ("%p: freed", mem); GST_DEBUG ("%p: freed", mem);
@ -85,6 +85,9 @@ gst_dmabuf_mem_map (GstMemory * gmem, gsize maxsize, GstMapFlags flags)
gint prot; gint prot;
gpointer ret = NULL; gpointer ret = NULL;
if (gmem->parent)
return gst_dmabuf_mem_map (gmem->parent, maxsize, flags);
g_mutex_lock (&mem->lock); g_mutex_lock (&mem->lock);
prot = flags & GST_MAP_READ ? PROT_READ : 0; prot = flags & GST_MAP_READ ? PROT_READ : 0;
@ -94,7 +97,7 @@ gst_dmabuf_mem_map (GstMemory * gmem, gsize maxsize, GstMapFlags flags)
if (mem->data) { if (mem->data) {
/* only return address if mapping flags are a subset /* only return address if mapping flags are a subset
* of the previous flags */ * of the previous flags */
if ((mem->mmapping_flags & prot) && (mem->mmap_size >= maxsize)) { if (mem->mmapping_flags & prot) {
ret = mem->data; ret = mem->data;
mem->mmap_count++; mem->mmap_count++;
} }
@ -103,7 +106,7 @@ gst_dmabuf_mem_map (GstMemory * gmem, gsize maxsize, GstMapFlags flags)
} }
if (mem->fd != -1) { if (mem->fd != -1) {
mem->data = mmap (0, maxsize, prot, MAP_SHARED, mem->fd, 0); mem->data = mmap (0, gmem->maxsize, prot, MAP_SHARED, mem->fd, 0);
if (mem->data == MAP_FAILED) { if (mem->data == MAP_FAILED) {
mem->data = NULL; mem->data = NULL;
GST_ERROR ("%p: fd %d: mmap failed: %s", mem, mem->fd, GST_ERROR ("%p: fd %d: mmap failed: %s", mem, mem->fd,
@ -116,7 +119,6 @@ gst_dmabuf_mem_map (GstMemory * gmem, gsize maxsize, GstMapFlags flags)
if (mem->data) { if (mem->data) {
mem->mmapping_flags = prot; mem->mmapping_flags = prot;
mem->mmap_size = maxsize;
mem->mmap_count++; mem->mmap_count++;
ret = mem->data; ret = mem->data;
} }
@ -134,12 +136,15 @@ gst_dmabuf_mem_unmap (GstMemory * gmem)
{ {
#ifdef HAVE_MMAP #ifdef HAVE_MMAP
GstDmaBufMemory *mem = (GstDmaBufMemory *) gmem; GstDmaBufMemory *mem = (GstDmaBufMemory *) gmem;
if (gmem->parent)
return gst_dmabuf_mem_unmap (gmem->parent);
g_mutex_lock (&mem->lock); g_mutex_lock (&mem->lock);
if (mem->data && !(--mem->mmap_count)) { if (mem->data && !(--mem->mmap_count)) {
munmap ((void *) mem->data, mem->mmap_size); munmap ((void *) mem->data, gmem->maxsize);
mem->data = NULL; mem->data = NULL;
mem->mmap_size = 0;
mem->mmapping_flags = 0; mem->mmapping_flags = 0;
GST_DEBUG ("%p: fd %d unmapped", mem, mem->fd); GST_DEBUG ("%p: fd %d unmapped", mem, mem->fd);
} }
@ -171,7 +176,7 @@ gst_dmabuf_mem_share (GstMemory * gmem, gssize offset, gssize size)
GST_MINI_OBJECT_FLAG_LOCK_READONLY, mem->mem.allocator, parent, GST_MINI_OBJECT_FLAG_LOCK_READONLY, mem->mem.allocator, parent,
mem->mem.maxsize, mem->mem.align, mem->mem.offset + offset, size); mem->mem.maxsize, mem->mem.align, mem->mem.offset + offset, size);
sub->fd = dup (mem->fd); sub->fd = -1;
g_mutex_init (&sub->lock); g_mutex_init (&sub->lock);
return GST_MEMORY_CAST (sub); return GST_MEMORY_CAST (sub);