On 11/25/2014 07:52 AM, Axel Davy wrote:
Hi,
Sorry for the late reply, seems my e-mail filters hate me - i was
already worried about the lack of replies.
This patch removes the tripple buffering behaviour that the GLX
implementation
has with DRI3. I understand your concern for Medical softwares,
but perhaps this would be better handled with an user option.
Axel Davy
I don't think it does that?
For swapinterval > 0 all the triple-buffering etc. is left active as
usual, and swaps are supposed to be vsynced and tear-free. swapinterval
is 1 by default, so this is the case by default.
For a client or user selected swapinterval = 0, the code in Mesa
schedules glXSwapBuffers calls to occur immediately, and the Present
implementation in the server schedules them in a way so they are
supposed to occur immediately/asap - assuming no vsync, otherwise the
logic there wouldn't make much sense.
Due to what i'm pretty sure is a bug (see my other 2 patches on top of
the xserver dri3/present implementation) the PresentOptionAsync isn't
handled correctly by the server for pagelfips as it should be, and as
result vsync is always on on intel-ddx, and always off on nouveau-ddx
(or any future driver which exposes PresentCapabilityAsync as nouveau
does), which causes massive tearing on nouveau all the time under
dri3/present.
On any os/graphics-stack i'm familiar with (Windows and OSX all versions
and drivers, Linux proprietary drivers, DRI2 with intel-ddx and
nouveau-ddx) a swapinterval zero meant to swap immediately without
vsync, so this just restores what probably any OpenGL client expects to
happen. The MESA_swap_control spec even states that "If <interval> is
set to a value of 0, buffer swaps are not synchronized to a video frame."
For medical or neuro-science applications like mine, or multi-display
stereo/VR applications it is crucial to have this for users being able
to easily diagnose multi-display synchronization issues without the need
to learn how to use git and compilers and how graphics stacks work. For
gamers and gaming benchmarks it's the "ego-shooter mode" and "squeeze
out max fps" they like so much.
Btw., digging deeper into the ddx'es i realized that my posted patch for
the x-server bug is both incomplete and too complex. I've written a new
patch which is only a simple one-liner but solves more problems than the
old one. I'll send it out after giving it some testing.
thanks,
-mario
On 25/11/2014 04:00, Mario Kleiner wrote :
Restores proper immediate tearing swap behaviour for
OpenGL bufferswap under DRI3/Present.
Cc: "10.3 10.4" <mesa-sta...@lists.freedesktop.org>
Signed-off-by: Mario Kleiner <mario.kleiner...@gmail.com>
---
src/glx/dri3_glx.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/src/glx/dri3_glx.c b/src/glx/dri3_glx.c
index 5796491..c53be1b 100644
--- a/src/glx/dri3_glx.c
+++ b/src/glx/dri3_glx.c
@@ -1518,6 +1518,7 @@ dri3_swap_buffers(__GLXDRIdrawable *pdraw,
int64_t target_msc, int64_t divisor,
xcb_connection_t *c = XGetXCBConnection(dpy);
struct dri3_buffer *back;
int64_t ret = 0;
+ uint32_t options = XCB_PRESENT_OPTION_NONE;
unsigned flags = __DRI2_FLUSH_DRAWABLE;
if (flush)
@@ -1557,6 +1558,9 @@ dri3_swap_buffers(__GLXDRIdrawable *pdraw,
int64_t target_msc, int64_t divisor,
if (target_msc == 0)
target_msc = priv->msc + priv->swap_interval *
(priv->send_sbc - priv->recv_sbc);
+ if (priv->swap_interval == 0)
+ options |= XCB_PRESENT_OPTION_ASYNC;
+
back->busy = 1;
back->last_swap = priv->send_sbc;
xcb_present_pixmap(c,
@@ -1570,7 +1574,7 @@ dri3_swap_buffers(__GLXDRIdrawable *pdraw,
int64_t target_msc, int64_t divisor,
None, /* target_crtc */
None,
back->sync_fence,
- XCB_PRESENT_OPTION_NONE,
+ options,
target_msc,
divisor,
remainder, 0, NULL);
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