1204160 - Implement a small object optimization for mozilla::Function

Status: RESOLVED INVALID

(Core :: MFBT, defect)

Description

[Botond Ballo [:botond] [away until Jun 24]]

Currently, mozilla::Function stores a UniquePtr to the object that stores the wrapped callable. This means every instance of mozilla::Function incurs a dynamic allocation.

We should consider implementing a small-object optimization, where if the size of the callable is smaller than a threshold (say, 16 bytes), the callable is stored in-line. libc++'s implementation of std::function does this. [1]

[1] https://github.com/llvm-mirror/libcxx/blob/6d9da5891f6628ffa9d2f382113a8231121aeee1/include/functional#L1564

Comment 1

[Simon Giesecke [:sg] [he/him]]

Bug 1320752 removed mozilla::Function in favor of std::function, so this seems obsolete.