On 08.01.2016 18:09, Ian Romanick wrote:
On 01/07/2016 04:57 PM, Nicolai Hähnle wrote:
From: Nicolai Hähnle <nicolai.haeh...@amd.com>
We will want to disable minmax index caching for buffers that are used in this
way.
I think this is too heavy handed. It seems like what you want is to
disable caching of draws in the mapped range while it is mapped. If an
app has a 16mb buffer, maps the last 8mb, unmaps it, then draws, it
would be a shame to lose the cache forever. To avoid having to do all
the range checking in the draw and cache-invalidate code, you could just
clear the USAGE_PERSISTENT_WRITE_MAP bit in the unmap. Right?
I like that idea. An alternative would be to just check the access flags
in the cache itself, i.e. an additional check like:
if (bufferObj->Mappings[MAP_USER].AccessFlags &
(GL_MAP_PERSISTENT_BIT | GL_MAP_WRITE_BIT) ==
(GL_MAP_PERSISTENT_BIT | GL_MAP_WRITE_BIT))
// don't use the cache
It's a few additional instructions in vbo_use_minmax_cache and a few
instructions less in _mesa_map_buffer_range. That's probably a good
trade-off, right?
Otherwise, perhaps the variable UsageHistory should be renamed if it
contains non-sticky flags...
Cheers,
Nicolai
---
src/mesa/main/bufferobj.c | 6 +++++-
src/mesa/main/mtypes.h | 1 +
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/src/mesa/main/bufferobj.c b/src/mesa/main/bufferobj.c
index 8fd9a06..ef2b495 100644
--- a/src/mesa/main/bufferobj.c
+++ b/src/mesa/main/bufferobj.c
@@ -2474,9 +2474,13 @@ _mesa_map_buffer_range(struct gl_context *ctx,
assert(bufObj->Mappings[MAP_USER].AccessFlags == access);
}
- if (access & GL_MAP_WRITE_BIT)
+ if (access & GL_MAP_WRITE_BIT) {
bufObj->Written = GL_TRUE;
+ if (access & GL_MAP_PERSISTENT_BIT)
+ bufObj->UsageHistory |= USAGE_PERSISTENT_WRITE_MAP;
+ }
+
#ifdef VBO_DEBUG
if (strstr(func, "Range") == NULL) { /* If not MapRange */
printf("glMapBuffer(%u, sz %ld, access 0x%x)\n",
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 9e4b2c8..4d625da 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -1255,6 +1255,7 @@ typedef enum {
USAGE_SHADER_STORAGE_BUFFER = 0x8,
USAGE_TRANSFORM_FEEDBACK_BUFFER = 0x10,
USAGE_PIXEL_PACK_BUFFER = 0x20,
+ USAGE_PERSISTENT_WRITE_MAP = 0x40,
} gl_buffer_usage;
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