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This disables for now the "optimistic" SIMD heuristic that was implemented for xe3+ and makes it dependent on a debugging option, instead use the static analysis-based codepath that was used in previous generations and was extended by previous commits in this MR to model the xe3 trade-off between register use and thread parallelism. The reason is that the main assumption of the optimistic SIMD heuristic didn't hold up with reality: Real-world testing on PTL shows that there are many cases where SIMD32 shows performance degradation relative to SIMD16 despite the ability of xe3 hardware to scale the GRF file of a thread on demand, unfortunately that scenario seems to be more pervasive than hoped when the optimistic SIMD heuristic was implemented pre-silicon. In many cases what seems to be going on is that even when the register file is able to scale with the increased register use of SIMD32, the thread parallelism of the EU is scaled down by a similar factor, so at the bottom line SIMD32 (depending on the actual ratio of register use between both variants) may not buy us anything, and it frequently encounters constraints (like SIMD lowering and less effective scheduling) that lead to worse codegen than SIMD16, easily tipping the balance in favor of SIMD16. The extension of the performance analysis pass that was done in a previous commit allows the original SIMD32 heuristic to take into account quantitatively this effect, and that seems pretty effective at disabling SIMD32 shaders that underperform judging from the statistically significant improvement of most Traci test-cases that run on my PTL system (4 iterations, 5% significance), no statistically significant regressions were observed: Nba2K23-trace-dx11-2160p-ultra: 10.16% ±0.34% Superposition-trace-dx11-2160p-extreme: 4.06% ±0.50% TotalWarWarhammer3-trace-dx11-1080p-high: 3.52% ±0.76% Payday3-trace-dx11-1440p-ultra: 2.41% ±0.81% MetroExodus-trace-dx11-2160p-ultra: 2.28% ±0.78% Borderlands3-trace-dx11-2160p-ultra: 1.89% ±0.65% MountAndBlade2-trace-dx11-1440p-veryhigh: 1.81% ±0.40% Blackops3-trace-dx11-1080p-high: 1.66% ±0.29% HogwartsLegacy-trace-dx12-1080p-ultra: 1.53% ±0.22% TotalWarPharaoh-trace-dx11-1440p-ultra: 1.44% ±0.31% Fortnite-trace-dx11-2160p-epix: 1.44% ±0.27% Naraka-trace-dx11-1440p-highest: 1.39% ±0.27% PubG-trace-dx11-1440p-ultra: 1.30% ±0.49% Destiny2-trace-dx11-1440p-highest: 1.10% ±0.23% Factorio-trace-1080p-high: 1.10% ±1.77% TerminatorResistance-trace-dx11-2160p-ultra: 1.08% ±0.31% Ghostrunner2-trace-dx11-1440p-ultra: 1.05% ±0.15% ShadowTombRaider-trace-dx11-2160p-ultra: 0.98% ±0.19% CitiesSkylines2-trace-dx11-1440p-high: 0.67% ±0.19% Palworld-trace-dx11-1080p-med: 0.44% ±0.22% The downside is that this will reverse the large reduction in compile-time we gained from the optimistic SIMD heuristic -- The run-time of both shader-db and fossil-db jump back up by nearly 20% with this change. I'm working on a better compromise based on run-time feedback that will hopefully allow us to preserve the compile-time benefit of the optimistic heuristic without the reduction in run-time performance, but in the meantime it seems like the run-time performance gap from SIMD32 is the more urgent issue to address since it has an impact on titles across the board. Despite the reversal of that compile-time improvement xe3 still achieves slightly lower compile time on the average than previous generations as a result of VRT, so this doesn't seem terribly tragic. v2: Add bit to brw_get_compiler_config_value() (Lionel). Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36618> |
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`Mesa <https://mesa3d.org>`_ - The 3D Graphics Library ====================================================== Source ------ This repository lives at https://gitlab.freedesktop.org/mesa/mesa. Other repositories are likely forks, and code found there is not supported. Build & install --------------- You can find more information in our documentation (`docs/install.rst <https://docs.mesa3d.org/install.html>`_), but the recommended way is to use Meson (`docs/meson.rst <https://docs.mesa3d.org/meson.html>`_): .. code-block:: sh $ meson setup build $ ninja -C build/ $ sudo ninja -C build/ install Support ------- Many Mesa devs hang on IRC; if you're not sure which channel is appropriate, you should ask your question on `OFTC's #dri-devel <irc://irc.oftc.net/dri-devel>`_, someone will redirect you if necessary. Remember that not everyone is in the same timezone as you, so it might take a while before someone qualified sees your question. To figure out who you're talking to, or which nick to ping for your question, check out `Who's Who on IRC <https://dri.freedesktop.org/wiki/WhosWho/>`_. The next best option is to ask your question in an email to the mailing lists: `mesa-dev\@lists.freedesktop.org <https://lists.freedesktop.org/mailman/listinfo/mesa-dev>`_ Bug reports ----------- If you think something isn't working properly, please file a bug report (`docs/bugs.rst <https://docs.mesa3d.org/bugs.html>`_). Contributing ------------ Contributions are welcome, and step-by-step instructions can be found in our documentation (`docs/submittingpatches.rst <https://docs.mesa3d.org/submittingpatches.html>`_). Note that Mesa uses gitlab for patches submission, review and discussions.