This had not been observed as an issue prior to
923705e514 because CMakeLists.txt had, until
then, been using EQUAL, not STREQUAL, to test for oe (and to then enable
USE_SMALL_CHUNKS). This test would fail, and so the default SLAB_SIZE was
used. Absent this min operation, the use of a whole page on a 64KiB page
causes a crash when using the largest medium size class, as, ultimately, size
classes are not based on page sizes, and so committing a whole page to the
header leaves too little room for that class.
See also 3d3b048776.
This change makes the original 16MiB option not the common option.
It also changes the names of the defines to
SNMALLOC_USE_LARGE_CHUNKS
SNMALLOC_USE_SMALL_CHUNKS
The second should be set for Open Enclave configuration, and results in
256KiB chunk sizes. The first being set builds the original 16MiB chunk
sizes. If neither is set, then we default to 1MiB chunk sizes.
* 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.
This does not deallocate memory until the OS tells us that we are short
on memory, then tries to decommit all of the cached chunks (except for
the first page, used for the linked lists).
Nowhere near enough testing to commit to master yet!
