Rewrite the multidrawable batch set builder for performance.#17923
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superdump merged 1 commit intobevyengine:mainfrom Feb 20, 2025
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This commit restructures the multidrawable batch set builder for better performance in various ways: * The bin traversal is optimized to make the best use of the CPU cache. * The inner loop that iterates over the bins, which is the hottest part of `batch_and_prepare_binned_render_phase`, has been shrunk as small as possible. * Where possible, multiple elements are added to or reserved from GPU buffers as a batch instead of one at a time. * Methods that LLVM wasn't inlining have been marked `#[inline]` where doing so would unlock optimizations. This code has also been refactored to avoid duplication between the logic for indexed and non-indexed meshes via the introduction of a `MultidrawableBatchSetPreparer` object. Together, this improved the `batch_and_prepare_binned_render_phase` time on Caldera by approximately 2×. Eventually, we should optimize the batchable-but-not-multidrawable and unbatchable logic as well, but these meshes are much rarer, so in the interests of keeping this patch relatively small I opted to leave those to a follow-up.
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Example runner looks good. |
IceSentry
approved these changes
Feb 19, 2025
tychedelia
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Feb 19, 2025
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tychedelia
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Thanks, the comments in the new implementation are really nice.
superdump
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Feb 20, 2025
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This commit restructures the multidrawable batch set builder for better performance in various ways:
The bin traversal is optimized to make the best use of the CPU cache.
The inner loop that iterates over the bins, which is the hottest part of
batch_and_prepare_binned_render_phase, has been shrunk as small as possible.Where possible, multiple elements are added to or reserved from GPU buffers as a batch instead of one at a time.
Methods that LLVM wasn't inlining have been marked
#[inline]where doing so would unlock optimizations.This code has also been refactored to avoid duplication between the logic for indexed and non-indexed meshes via the introduction of a
MultidrawableBatchSetPreparerobject.Together, this improved the
batch_and_prepare_binned_render_phasetime on Caldera by approximately 2×.Eventually, we should optimize the batchable-but-not-multidrawable and unbatchable logic as well, but these meshes are much rarer, so in the interests of keeping this patch relatively small I opted to leave those to a follow-up.