This will let us use Pagemaps further down the dependency stack (specifically,
we're going to want a Pagemap inside the AddressSpaceManager) by letting us
manually tie the knot rather than rely on GlobalVirtual and
default_memory_provider() being defined by the time we want a Pagemap.
Presently, GlobalPagemap and ExternalPagemap discriminate only by type. If it
ever happened that multiple PageMap consumers instantiated the same type using
these wrapper, they'd be conflated in the symbol table. Therefore, add an
optional Purpose parameter that will be expanded into the symbols (but serves no
other purpose).
- Make GlobalPagemapTemplate and ExternalGlobalPagemap generic in the type of
the pagemap they're encapsulating.
We're going to want to use these for other kinds of pagemaps in the near
future.
- Rename snmalloc_pagemap_global_get to snmalloc_chunkmap_global_get.
- Rename GlobalPagemap to GlobalChunkmap.
MSVC has strong opinions on implicit conversions as used in CI, while Clang both
locally and in CI has weaker opinions. In an effort to avoid subsequent
roundtrips through CI, make clang more strict. Adding -Wconversion definitely
increases the strength of clang's opinions, apparently to include frowning on
some that even MSVC considers OK, so go make explicit the current implicit
behavior.
Presently, our flat pagemap can be configured to take...
32-bit AS 48-bit AS
USE_SMALL_CHUNKS 16 KiB 1 GiB
default 4 KiB 256 MiB
USE_LARGE_CHUNKS 256 B 16 MiB
At 1 GiB, we're already past the 512 MiB threshold imposed when
src/test/func/memory/memory.cc, when configured to TEST_LIMITED, probes the
effect of rlimit.
Instead, restrict flat pagemaps to at most 256 MiB of AS by default (override
by defining SNMALLOC_MAX_FLATPAGEMAP_SIZE), which forces the USE_SMALL_CHUNKS &
48-bit AS configuration to use the tree-based version.
While here, rename USE_FLATPAGEMAP to CHUNKMAP_USE_FLATPAGEMAP.
There are two things calling themselves pagemaps:
- the src/mem/pagemap.h objects of that name
- the SuperslabMap object gets called a PageMap inside the Allocator
Rename the latter to chunkmap, with appropriate case and snake,
everywhere, and pull it out to its own file (chunkmap.h).
The default implementation of a chunkmap is a purely static object, but
we nevertheless instantiate it per allocator, so that other
implementations can use stateful instances when interposing on the
mutation methods. Note that the "get" method, however, must remain
static to support the interface required by Allocator objects.
