* Increase Remote batch size
The remote batch size has not changed since the fast path optimisations.
The optimisations mean we are checking the queue considerably less
often, so the batch should be larger. This has a dramatic improvement
on performance on a few of the mimalloc microbenchmarks.
It is set to 4096 as this should cover the worse case scenario of only
remote deallocation at 16 bytes for the 2^16 slab size.
* Fixes for Clang-10
Clang-10 outputs a warning for calling alignment intrinsic with an
alignment of 1. At add constexpr to handle this case.
Improve remote dealloc
- Outline the slow path to improve code gen significantly
- Handle message queue only on slow path for remote dealloc.
- Change remote size to count down 0, so fast path does not need a constant.
- Use signed value so that branch does not depend on addition.
The bootstrapping allocator needs to perform a memcpy to bypass the
removed move constructors on std::atomic. This is safe as there is no
concurrency at this point, but GCC is unhappy with this.
This commit moves CI to GCC8 and disables this warning for that line.
The readme was considerably out of date, with the introduction
being over a year old. This commit reflects the developments and
improvements in stabiity of snmalloc.
On platforms that support low-memory notifications register callbacks
that perform lazy decommit. This allows idle processes to return memory
to the OS. Without incurring the cost of constantly committing and
decommitting memory.
Code review and CI changes
* Fixed test to use a template to make constexpr magic work
* Factored out basic notification mechanism so can be reused on other
platforms.
If the external thread statics are used, then
we don't need to include some C++ runtime
concepts. This refactoring moves some global initialization under
conditional compilation.
