[ET-VK] Allocate memory for weight and activation tensors lazily#13500
Closed
pytorchbot wants to merge 1 commit intogh/SS-JIA/291/origfrom
Closed
[ET-VK] Allocate memory for weight and activation tensors lazily#13500pytorchbot wants to merge 1 commit intogh/SS-JIA/291/origfrom
pytorchbot wants to merge 1 commit intogh/SS-JIA/291/origfrom
Conversation
Pull Request resolved: #13474 * Allocate memory for weight tensors right before the prepacking shader is dispatched, rather than while building the graph * Move allocation of shared objects (i.e. memory for intermediate tensors) to occur after prepacking ## Motivation Prevent screen blackout (Llama 3.2 1B) / device crash (Llama 3.2 3B) when running Llama 3.2 models on Samsung Galaxy S24. This behaviour is related to high peak memory usage when loading the model. ## Full Context During model loading, Vulkan delegate needs to store 3 copies of constant data in memory at various points: * source data obtained from loading the model * staging buffer * GPU texture/buffer The general rationale of this change is to allocate memory for each copy only when necessary to minimize the "overlap" when all 3 exist at once. ### Current Order of operations Legend: * `W` represents total weight nbytes * `w` represents weight nbytes for one tensor * `A` represents total activations nbytes * `M` represents approximation of total memory footprint First, model file is loaded Then, when building compute graph, for each weight tensor: 1. Weight data is loaded from NamedDataMap (`M = W`) 2. GPU texture/buffer for weight is initialized + memory allocated (`M = 2W`) 3. After building the graph, `graph->prepare()` is called which currently allocates memory for the activation tensors as well (`M = 2W + A`) Then, during the prepacking stage for each weight tensor, each weight tensor is copied individually: 1. Staging buffer initialized (`M = 2W + A + w`) 2. Copy CPU weight data to staging + CPU Weight data is freed (`M = 2W + A`) 3. Compute shader dispatch to copy staging to GPU texture/buffer + free staging buffer (`M = 2W + A - w`) The peak usage in mainline will be `M = 2W + A + w` ### Revised order of operations This change revises the order of operations: 1. Weight data is loaded from NamedDataMap (`M = W`) 2. GPU texture/buffer for weight is initialized, but **memory is not allocated** (`M = W`) Then, during the prepacking stage for each weight tensor, each weight tensor is copied individually: 1. Staging buffer initialized (`M = W + w`) 2. **Memory allocated for GPU texture/buffer** (`M = W + 2w`) 3. Copy CPU weight data to staging + CPU Weight data is freed (`M = W + w`) 4. Compute shader dispatch to copy staging to GPU texture/buffer + free staging buffer (`M = W`) **Then, after all prepacking operations complete, only then is Activation memory allocated** (`M = W + A`) Under this scheme, peak memory is reduced to `M = W + A` (or alternatively `M = W + 2w` if `2w > A`) which is (or at least very close to) the theoretical minimum. ghstack-source-id: 303862303 Differential Revision: [D80460033](https://our.internmc.facebook.com/intern/diff/D80460033/)
🔗 Helpful Links🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/13500
Note: Links to docs will display an error until the docs builds have been completed. ✅ You can merge normally! (1 Unrelated Failure)As of commit 6c18621 with merge base 5ff0208 ( BROKEN TRUNK - The following job failed but were present on the merge base:👉 Rebase onto the `viable/strict` branch to avoid these failures
This comment was automatically generated by Dr. CI and updates every 15 minutes. |
meta-cla
Bot
added
the
CLA Signed
An error occurred while trying to automatically change base from
gh/SS-JIA/291/orig
to
main
August 19, 2025 03:06
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
This PR was created by the merge bot to help merge the original PR into the main branch.
ghstack PR number: #13474 by @SS-JIA
^ Please use this as the source of truth for the PR details, comments, and reviews
ghstack PR base: https://github.com/pytorch/executorch/tree/gh/SS-JIA/292/base
ghstack PR head: https://github.com/pytorch/executorch/tree/gh/SS-JIA/292/head
Merge bot PR base: https://github.com/pytorch/executorch/tree/gh/SS-JIA/291/orig
Merge bot PR head: https://github.com/pytorch/executorch/tree/gh/SS-JIA/292/orig
@diff-train-skip-merge