tree 4aea0afada6171e456ea84f5826e2741247ec819
parent b141bf9b1ea19272fde0cfbbdc7888d3f16526ac
author Protobuf Team Bot <protobuf-github-bot@google.com> 1668545879 -0800
committer Copybara-Service <copybara-worker@google.com> 1668799052 -0800

In arena, allocate strings on dedicated string blocks so that they can be efficiently destructed.

- StringBlocks form a chunked linked list in which all nodes other than the first are full. When sizeof(void*)==8 and sizeof(std::string)==24, there are 21 strings per 512 byte StringBlock.
- We no longer need to store cleanup nodes for std::string (when using AllocateAlignedWithCleanup) - instead we traverse the StringBlock list.
- Template AllocAligned on is_string in order to avoid comparing the destructor against the string destructor on the allocation hot path.
- Remove specialized cleanup blocks for string/cord. This allows for simplifying the allocation and cleanup code, and we still save memory due to no longer needing cleanup nodes for most strings.

PiperOrigin-RevId: 488736123