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[TRTLLM-11412][fix] Preserve dense tensor layouts during offloading - #18539
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Signed-off-by: Rahul Steiger <rahul-steiger-nv@users.noreply.github.com>
Signed-off-by: Rahul Steiger <rsteiger@nvidia.com>
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Included review availability: Your plan provides up to 12 included reviews per hour; 11 remain after this review. WalkthroughOffloading now accepts dense tensors with non-contiguous strides. It rejects overlapping or non-dense tensors. CPU packing preserves physical storage order. Tests verify channels-last-3D stride and value preservation. ChangesDense tensor offloading
Priority: ⬇️ Low Estimated code review effort: 2 (Simple) | ~10 minutes Change: Bug fix Suggested reviewers: Merge Risk: 🔵 Low · up to The change targets preserving values and strides for dense non-contiguous tensors while rejecting unsupported layouts. The remaining test-annotation issue does not affect runtime behavior, so merge risk is low. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
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Inline comments:
In `@tests/unittest/_torch/visual_gen/test_offloading.py`:
- Around line 359-377: Add the explicit None return annotation to the
test_offload_preserves_channels_last_3d_layout test function, preserving its
existing test logic.
Apply the same fix in `@tests/unittest/_torch/visual_gen/test_offloading.py` at
line 359.
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LGTM. The three pieces line up:
_is_non_overlapping_and_denseis the standard predicate (sort(stride, size), skip size<=1 dims, require the recurrence1, n0, n0*n1, ...). It admits any dense permutation and still rejectsexpand-style overlap and strided gaps. I hand-checked it against Conv3d weights with size-1 kernel dims, e.g.(96, 96, 1, 3, 3)-> strides(864, 1, 864, 288, 96), where the size-1 dim's stride is correctly ignored.as_strided((numel,), (1,))copies the dense span from the tensor's ownstorage_offset(as_stridedinherits it whenstorage_offset=None), which is exactlyspec.nbytes. This is the real fix:reshape(-1)materialized a copy in logical order, which then got reinterpreted with the physical stride at rebind time._make_viewsrestoresspec.strideat the packed offset, andstage()is a raw byte copy of the whole stage buffer, so the layout survives the GPU transfer too.
Aliasing still behaves: two permuted views of one storage copy identical raw bytes, and each is rebound with its own stride.
One minor, non-blocking comment inline about the untested rejection branch.
Two notes:
- The auto-generated summary in the description says "No
tests/integration/test_lists/coverage entry was identified. Verdict: needs follow-up." That looks incorrect -tests/integration/test_lists/test-db/l0_b200.yml:286lists the whole fileunittest/_torch/visual_gen/test_offloading.py, sotest_offload_preserves_channels_last_3d_layoutis collected in l0_b200. No follow-up needed there. - Nit on the new docstring: the tensor densely covers a contiguous span starting at its
storage_offset, not "its storage" - a slice of a larger allocation passes the check, and should.
Disclosure: I reviewed by reading as_strided/narrow/view semantics and hand-evaluating the stride recurrence; I did not execute the new test locally.
Signed-off-by: Rahul Steiger <rsteiger@aws-cmh-slurm-1-vscode-04.cm.cluster>
…x/visual-gen-offload-channels-last
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Signed-off-by: Rahul Steiger <rsteiger@nvidia.com>
…x/visual-gen-offload-channels-last
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Signed-off-by: Rahul Steiger <rsteiger@nvidia.com>
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Inline comments:
In `@tensorrt_llm/_torch/visual_gen/offloading.py`:
- Around line 187-189: Update ModuleOffloadManager’s tensor validation around
_is_non_overlapping_and_dense and _append_layout_spec to reject separately
registered tensor views whose storage ranges partially overlap, unless the
implementation preserves their shared storage and original offsets. Ensure
overlapping channels-last views cannot be packed into independent ranges, and
add a regression test verifying aliasing remains intact after initialization and
staging.
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Description
Fixes NVBug 6702264.
Allow the offload manager to pack non-overlapping dense tensors such as Wan VAE
channels_last_3dweights. Tensor bytes are copied in physical storage order sothe original strides and values are preserved when CPU and GPU views are rebound.
Overlapping and non-dense layouts remain unsupported.
Dev Engineer Review
channels_last_3dlayouts.QA Engineer Review
tests/unittest/_torch/visual_gen/test_offloading.py.channels_last_3dvalue and stride preservation.test-db/orqa/lists.ci: full pre-merge approvedlabel and a CI re-run.Per-File QA Perspective
tensorrt_llm/_torch/visual_gen/offloading.py: Verify dense tensors preserve values and strides during CPU and GPU staging. Verify unsupported layouts remain rejected.tests/unittest/_torch/visual_gen/test_offloading.py: Coverschannels_last_3dpreservation and invalid-layout rejection. The test was not found in the inspected CI or manual-QA lists.Test Coverage
test_offload_preserves_channels_last_3d_layoutto verify values andstrides after initialization and staging.
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