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.
Though a new implementation is in the works, roll in
some performance improvements in the mean time.
The probe routines have been broken out into separate
reader/writer variants. These variants are much less
branch-intensive (and don't involve predict to stall
in many cases).
New implementation is attempting to deal with
interface-induced overheads.
Documentation and regressions tests have been updated to reflect this.
This functionality allows for individual hash tables use to different
allocation functions. Thanks to Wez Furlong for pointing out the necessary
documentation update for ck_ht.
Specifically, any platform that has CK support for 64-bit
load/store operations.
Additional improvements have been made to the unit tests
to disambiguate put/get failures.
This is a hash table that is optimized for architectures that
implement total store ordering and workloads that are read-heavy
involving a single writer and multiple readers. Unlike traditional
non-blocking multi-producer/multi-consumer hash table
implementations this version allows for immediate re-use of deleted
buckets (no need for explicit reclamation cycles) and is more
conducive to traditional safe memory reclamation schemes used in
unmanaged languages (otherwise, we would require key duplication).
It is relatively heavy-weight for MPMC workloads on architectures
which do not implement TSO in comparison to Click's MPMC hash
table. However, it still has better performance characteristics
than a blocking hash table.
The committed version currently only provides x86_64 support. This is
being committed for review by peers and for a silent release that will
allow us to test ck_ht_spmc under high production workloads.
Next public release will include additional documentation as well as
support for other architectures.
In the mean time, please see the unit tests for example usage. Included in
this commit: Dropped -Wbad-function-cast from GCC port.
Samy Al Bahra
Samy Al Bahra
William Irwin