pytorch

99d7c8ff - [caffe2] use AddNAlreadyReserved() when serializing blobs (#53400)

[caffe2] use AddNAlreadyReserved() when serializing blobs (#53400) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/53400 This is a reland of D26617038 (https://github.com/pytorch/pytorch/commit/b4a8d98247c4eac60ae594ae626886408dc4e2c0) after rebasing onto D26802576 (https://github.com/pytorch/pytorch/commit/f595ba1bae9a75c6403e4624e7294b5635acd40c). Optimize the blob serialization code by using `AddNAlreadyReserved()` when serializing tensor data, rather than making N separate `Add()` calls. `AddNAlreadyReserved()` is a simple addition operation, while each `Add()` call checks to see if it needs to reserve new space, and then updates the element data, which is unnecessary in this case. ghstack-source-id: 123567030 Test Plan: This appears to improve raw serialization performance by 30 to 35% for float, double, and int64_t types which use this function. This improvement appears relatively consistent across large and small tensor sizes. Reviewed By: mraway Differential Revision: D26853941 fbshipit-source-id: 4ccaa5bc1dd7f7864068d71a0cde210c699cbdba