The array is optimized for SPMC and fast iteration (though MPMC
transformation is also possible). This is an extremely simple
implementation with support for atomic in-place modification
through put -> remove elimination.
This operation moves ownership from one hash set object
to another and re-assigns callback functions to developer-specified
values. This allows for dynamic configuration of allocation
callbacks and is necessary for use-cases involving executable code
which may be unmapped underneath the hash set.
The developer is responsible for enforcing barriers and enforcing
the visibility of the new hash set.
It is possible for a defragmenting set or swap operation
to set a tombstone. If the probe sequence does not encounter
an empty slot and hits maximum write-side probe limit first
for it to fail to reprobe defragmenting store.
This function allows for explicit execution of all
deferred callbacks in an epoch_record. The primary
motivation is currently for performance profiling
but there are other use-cases where best-effort
semantics could be applied.
This is similar to the set of changes done to ck_ht.
In addition to this, a bug was caught were minimal
probe sequence was based on last rather than first
tombstone observed.
This hashset will now face long-running bursty
write -> delete -> write workloads much more effectively
and includes significant performance improvements for
delete heavy workloads (at least 2x measured).
Previously, a probe to an empty slot was necessary in order
to avoid hash table growth. As long as a tombstone is available,
re-use it. This prevents excessive growth on workloads involving
long bursts of writes (near 0.5 load factor) followed by long
bursts of deletes.
The distinction between additive/exponential implementation
and geometric implementation does little but confuse users.
The terminology used in ck_backoff now reflects terminology
used in literature.
ck_backoff_gb has been removed.
Samy Al Bahra
Samy Al Bahra
Abel Mathew