can we disable HDP flushes and other flushes for
USWC when we don't use write
combining and CPU writes to VRAM?
Nope, write combining happens in the CPU before the write request is
send over the PCIe bus.
The HDP is a (rather small) read/write cache in GPUs memory controller
as far as I know.
Regards,
Christian.
On 06.08.2015 17:09, Marek Olšák wrote:
On a related note, can we disable HDP flushes and other flushes for
USWC when we don't use write
combining and CPU writes to VRAM? Maybe by adding a per-IB flag that
would instruct the
kernel to flush or not flush HDP?
Marek
On Wed, Aug 5, 2015 at 4:18 AM, Michel Dänzer <mic...@daenzer.net> wrote:
On 03.08.2015 21:36, Marek Olšák wrote:
From: Marek Olšák <marek.ol...@amd.com>
---
src/gallium/drivers/radeon/r600_buffer_common.c | 6 ++++--
src/gallium/drivers/radeon/r600_pipe_common.c | 1 +
src/gallium/drivers/radeon/r600_pipe_common.h | 1 +
3 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/src/gallium/drivers/radeon/r600_buffer_common.c
b/src/gallium/drivers/radeon/r600_buffer_common.c
index fc5f6c2..d5ee188 100644
--- a/src/gallium/drivers/radeon/r600_buffer_common.c
+++ b/src/gallium/drivers/radeon/r600_buffer_common.c
@@ -111,7 +111,8 @@ bool r600_init_resource(struct r600_common_screen *rscreen,
switch (res->b.b.usage) {
case PIPE_USAGE_STREAM:
- flags = RADEON_FLAG_GTT_WC;
+ if (!(rscreen->debug_flags & DBG_NO_WC))
+ flags = RADEON_FLAG_GTT_WC;
/* fall through */
case PIPE_USAGE_STAGING:
/* Transfers are likely to occur more often with these
resources. */
@@ -133,7 +134,8 @@ bool r600_init_resource(struct r600_common_screen *rscreen,
default:
/* Not listing GTT here improves performance in some apps. */
res->domains = RADEON_DOMAIN_VRAM;
- flags |= RADEON_FLAG_GTT_WC;
+ if (!(rscreen->debug_flags & DBG_NO_WC))
+ flags |= RADEON_FLAG_GTT_WC;
break;
}
I think it would be both simpler and safer to mask out
RADEON_FLAG_GTT_WC after all the code which sets the various flags.
--
Earthling Michel Dänzer | http://www.amd.com
Libre software enthusiast | Mesa and X developer
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