On 02/29/2012 08:17 AM, Ben Skeggs wrote:
On Thu, 2012-02-16 at 00:45 +0100, Mario Kleiner wrote:
Hi,
Hey Mario,
What's your plan with this patchset? Do you intend on taking Michel's
comments into account?
CC'ing Francisco as he had some comments on IRC. I'd like to get this
all sorted and merged so I can rebase the ported-to-new-libdrm ddx on
top of it all and get that ready.
Hi Ben,
just sent out two updated patches wrt. to Michels feedback.
[1/10] Replaces the original [1/9] patch. The code is the same, but the
commit message is changed to be less misleading about the cause of the
problem. See the e-mail i think i sent about a week ago.
[10/10] Just for demonstration what i tried, not for application. The
old [9/9] patch is still the best i can do at the moment. Following
Michels proposal, with 10/10 i added refcounting to nouveau_dri2_buffer
objects and keep a reference while the swap is still pending. This
prevents deletion of the buffer by the x-server and thereby prevents the
server crash.
Problem: Now we have a display that doesn't crash, but flickers horribly
while pageflipping with deferred swaps. I think it is because we still
only have two buffers for double-buffering but pretend we're doing
triple-buffering, but i could be totally wrong about the cause of the
problem. The original patch [9/9] throttles the client in the special
case where the pseudo-triplebuffering would result in flicker or crash,
so it fixes the problem although in a rather hackish way.
Not sure if this can be done cleanly without a real n-buffering
implementation in the x-server?
I think other than that there were no further comments and Francisco's
original feedback from last year is already implemented in the patchset.
More feedback etc. welcome, but i usually can only work on this part
time on weekends if it needs further improvements before merging.
Can the kms kernel patches be already merged? I think they are in a good
shape now.
Thanks,
-mario
Ben.
here a set of patches against the nouveau-ddx. This is an extended and
revised set, based on Francisco Jerez feedback from autumn last year.
[1/9] Makes pageflipping work again on X-Server 1.12rc. It apparently stopped
working somewhere around Xorg 1.11+.
[2/9] Implements handling of pageflip completion events from the kernel.
Francisco Jerez argument against including it was that the x-server didn't
have a swaplimit api, so this couldn't be applied at the same time as the
pseudo triple-buffering hack which is in place in the current ddx.
Now we have the swaplimit api in 1.12, so this problem should be solved.
[3/9] Makes use of the swaplimit api. A new xorg.conf option "SwapLimit"
allows to select a swaplimit of 1 or 2 for double-buffering or
triple-buffering. It defaults to 2 for Xorg 1.12+ and 1 for older servers.
This way, on 1.12+ nouveau retains the kind of triple buffering behaviour it
currently has, but swap completion timestamping (OML_sync_control,
INTEL_swap_events, and client swap throttling) works conforming to
the specs. On older servers it removes triple-buffering but makes
nouveau conform to the specs. This is important for apps that need
precise and reliable swap scheduling and timestamping.
[4/9] A bug fix against corrupted desktop when switching from redirected
to non-redirected fullscreen windows under a desktop compositor.
Fixes FDO bug #35452.
[5/9] Some fixes to swap scheduling, revised according to Francisco's
review.
[6/9] Fixes swap throttling for non-fullscreen windows under a desktop
compositor. Split into a separate patch according to Francisco's
feedback.
[7/9] An attempt to provide more sane swap completion events for non-
fullscreen windows. This is a bit of cheating, as it delivers the
events for the earliest point in time one would expect the swap
to complete, assuming only a lightly loaded gpu. Real completion
could be later. I think this is an "improvement" because the current
implementation delivers swap complete events with timestamps and
counts that signal swap completion before the client even requested
the swap.
[8/9] This one adds Francisco's original triple-buffering hack back
for Xorg 1.11 and earlier servers if the xorg.conf option requests
a swaplimit> 1. Users can choose between "triple-buffering" but
broken timestamping or double-buffering with sane timestamping.
[9/9] Fixes a corner case which could cause the ddx to segfault
with its current triple-buffering implementation.
I've tested these on single-display and dual-display setups,
with/without compositor, with/without redirection and checked
the robustness and precision of the timestamps with special
measurement equipment, on XOrg 1.12-rc2 and 1.10. They work
pretty well for me and finally make nouveau very useable for
the kind of scientific applications that require precise
swap scheduling and timestamping, so i'd love to see them
reviewed and hopefully included into the ddx soon.
A couple of things are a bit of hacks:
[3/9] I think the setup of a default swap limit would be
better done in the x-server itself instead of the ddx. The
setup code is a bit awkward, hijacking the ddx->CreateBuffer
function to apply the swaplimit. A DRI2GetSwapLimit() function
is also missing from the server, which could help in the
future to track swaplimit changes by other clients than the ddx
itself. Unfortunately it is too late for the 1.12 release to do
this.
[8/9] Don't know if this is still wanted/needed or not?
[9/9] It fixes the problem and doesn't affect performance, but is
somewhat of a hack. I don't know how to do better, maybe somebody
else has a better solution?
Thanks,
-mario
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