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Move to FreeObject::T<capptr::bound<>>

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FreeObject itself is now just a namespace (but `friend`-ly); the actual free
list nodes are FreeObject::T-s that are templatized on the (perceived)
`capptr::bound<>` of the pointer they contain.  (These may differ across an
instantiated snmalloc; for example, in the sandboxing design, the in-sandbox
allocators may perceive all remotes to be full of `AllocUser` while the
privileged allocator of sandbox memory should perceive its remote queue as
holding `AllocUserWild` pointers in need of domestication.)

The interfaces to `FreeObject::T`-s now let us distinguish between the base and
inductive cases of the queues:

* in the inductive case, the pointer we hold to a `FreeObject::T` and its
  next_object have the same bounds

* in the base case, the pointer we hold has different bounds (typically,
  domesticated by contrast to the wild pointers in the queues).

To keep the clutter down a bit, we occasionally use raw pointers when we can be
reasonably certain that domestication is assured.  Moreover, we define some type
aliases, `FreeObject::{HeadPtr, QueuePtr, AtomicQueuePtr}`, that are slightly
more convenient labels than, e.g., `CapPtr<FreeObject::T<BQueue>, BView>`.
Because we are using template parameters for the `capptr::bound<>`s themselves,
we cannot use the aliases for `CapPtr<>s` provided within `capptr::`.

The two primary interfaces around free objects (`FreeListIter` AND
`FreeListBuilder`) are adjusted appropriately and their `BView` and `BQueue`
template paramters are plumbed explicitly around the tree.  This makes for quite
a bit of noise at the moment, but means that we'll be able to evolve parts of
the tree separately and can consider putting defaults in once that's done.
This commit is contained in:
Nathaniel Wesley Filardo
2021-09-17 14:32:14 +01:00
committed by Nathaniel Wesley Filardo
parent d76f5fdd28
commit e25db7b832
7 changed files with 391 additions and 169 deletions
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13
src/mem/localcache.h
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@@ -12,8 +12,9 @@ namespace snmalloc
{
using Stats = AllocStats<NUM_SIZECLASSES, NUM_LARGE_CLASSES>;
inline static SNMALLOC_FAST_PATH void*
finish_alloc_no_zero(capptr::AllocFull<FreeObject> p, sizeclass_t sizeclass)
inline static SNMALLOC_FAST_PATH void* finish_alloc_no_zero(
FreeObject::HeadPtr<capptr::bounds::AllocFull, capptr::bounds::AllocFull> p,
sizeclass_t sizeclass)
{
SNMALLOC_ASSERT(Metaslab::is_start_of_object(sizeclass, address_cast(p)));
UNUSED(sizeclass);
@@ -24,8 +25,9 @@ namespace snmalloc
}
template<ZeroMem zero_mem, typename SharedStateHandle>
inline static SNMALLOC_FAST_PATH void*
finish_alloc(capptr::AllocFull<FreeObject> p, sizeclass_t sizeclass)
inline static SNMALLOC_FAST_PATH void* finish_alloc(
FreeObject::HeadPtr<capptr::bounds::AllocFull, capptr::bounds::AllocFull> p,
sizeclass_t sizeclass)
{
auto r = finish_alloc_no_zero(p, sizeclass);
@@ -46,7 +48,8 @@ namespace snmalloc
// Free list per small size class. These are used for
// allocation on the fast path. This part of the code is inspired by
// mimalloc.
FreeListIter small_fast_free_lists[NUM_SIZECLASSES];
FreeListIter<capptr::bounds::AllocFull, capptr::bounds::AllocFull>
small_fast_free_lists[NUM_SIZECLASSES];
// This is the entropy for a particular thread.
LocalEntropy entropy;