[Pytorch Mobile] Remove caching (in code) of interned strings #50390
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Currently, there is a massive switch/case statement that is generated in the `InternedStrings::string()` method to speed up Symbol -> string conversion without taking a mock (mutex). The relative call rate of this on mobile is insignificant, so unlikely to have any material impact on runtime even if the lookups happen under a lock. Plus, parallelism is almost absent on mobile, which is where locks/mutexes cause the most problem (taking a mutex without contention is usually very fast and just adds a memory barrier iirc). The only impact that caching interned strings has is avoiding taking a lock when interned strings are looked up. They are not looked up very often during training, and based on basic testing, they don't seem to be looked up much during inference either. During training, the following strings were looked up at test startup: ``` prim::profile prim::profile_ivalue prim::profile_optional prim::FusionGroup prim::TypeCheck prim::FallbackGraph prim::ChunkSizes prim::ConstantChunk prim::tolist prim::FusedConcat prim::DifferentiableGraph prim::MMBatchSide prim::TensorExprGroup ``` Command used to trigger training: `buck test fbsource//xplat/papaya/client/executor/torch/store/transform/feature/test:test` During inference, the only symbol that was looked up was `tolist`. Differential Revision: [D25861786](https://our.internmc.facebook.com/intern/diff/D25861786/) [ghstack-poisoned]
💊 CI failures summary and remediationsAs of commit 6f9ec98 (more details on the Dr. CI page): 💚 💚 Looks good so far! There are no failures yet. 💚 💚 This comment was automatically generated by Dr. CI (expand for details).Follow this link to opt-out of these comments for your Pull Requests.Please report bugs/suggestions to the (internal) Dr. CI Users group. This comment has been revised 3 times. |
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Currently, there is a massive switch/case statement that is generated in the `InternedStrings::string()` method to speed up Symbol -> string conversion without taking a mock (mutex). The relative call rate of this on mobile is insignificant, so unlikely to have any material impact on runtime even if the lookups happen under a lock. Plus, parallelism is almost absent on mobile, which is where locks/mutexes cause the most problem (taking a mutex without contention is usually very fast and just adds a memory barrier iirc). The only impact that caching interned strings has is avoiding taking a lock when interned strings are looked up. They are not looked up very often during training, and based on basic testing, they don't seem to be looked up much during inference either. During training, the following strings were looked up at test startup: ``` prim::profile prim::profile_ivalue prim::profile_optional prim::FusionGroup prim::TypeCheck prim::FallbackGraph prim::ChunkSizes prim::ConstantChunk prim::tolist prim::FusedConcat prim::DifferentiableGraph prim::MMBatchSide prim::TensorExprGroup ``` Command used to trigger training: `buck test fbsource//xplat/papaya/client/executor/torch/store/transform/feature/test:test` During inference, the only symbol that was looked up was `tolist`. Differential Revision: [D25861786](https://our.internmc.facebook.com/intern/diff/D25861786/) ghstack-source-id: 119679831 Pull Request resolved: #50390
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This pull request has been merged in af968cd. |
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Stack from ghstack:
Currently, there is a massive switch/case statement that is generated in the
InternedStrings::string()method to speed up Symbol -> string conversion without taking a mock (mutex). The relative call rate of this on mobile is insignificant, so unlikely to have any material impact on runtime even if the lookups happen under a lock. Plus, parallelism is almost absent on mobile, which is where locks/mutexes cause the most problem (taking a mutex without contention is usually very fast and just adds a memory barrier iirc).The only impact that caching interned strings has is avoiding taking a lock when interned strings are looked up. They are not looked up very often during training, and based on basic testing, they don't seem to be looked up much during inference either.
During training, the following strings were looked up at test startup:
Command used to trigger training:
buck test fbsource//xplat/papaya/client/executor/torch/store/transform/feature/test:testDuring inference, the only symbol that was looked up was
tolist.Differential Revision: D25861786