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.
Writer-side synchronization is still necessary. My current use-cases call for
SLIST and LIST implementations, and as such, I've only implemented support
for these. TAILQ facilities will be developed when the time comes that I require
them or if there is sufficient user-demand.
Several users in the past have noted it was difficult for them
to decide what spinlock implementation to use. In light of this,
a light-weight greedy default is chosen (currently ck_spinlock_fas).
build:
- configure step will generate relevant CFLAGS.
- build profiles are for convenience (developers can use themu
for cross-compilation).
regressions:
- Renamed ck_barrier unit tests to work-around behavior
of Solaris linker.
- Adopted use of a PTHREAD_CFLAGS variable.
ck_cc:
- Added internal CK_CC_IMM macro for compilers that are
verbose against impossible inline constraints (or limited
optimizers).
ck_pr/x86*:
- Adopted CK_CC_IMM macro.
- Dropped redundant constraints.
This work was mostly completed by Theo Schlossnagle
<jesus@omniti.com>, much thanks to him. He has
also provided access to a machine with Sun Studio 12.
ck_epoch_reclaim is now the replacement for ck_epoch_flush.
ck_epoch_purge guarantees that all entries are reclaimed
for the provided record before exiting.
n_peak counter has been added, which provides the peak number
of items across all reclamation lists. n_reclamations provides
the number of reclamations across the lifetime of the record.
These are cleared on unregister.
ck_epoch_update has been renamed to ck_epoch_tick.
Hazardous sections which mutate shared structures are now
expected to begin with ck_epoch_write_begin and end with
ck_epoch_end.
Hazardous sections which read shared structures are now
expected to begin with ck_epoch_read_begin and end with
ck_epoch_end.
ck_hp_free is now more aggressive. It will attempt a
reclamation cycle any time the pending count is long.
I should probably add a ck_hp_retire to have a version
which allows for bulk updates to local reclamation lists.
The barriers have been restructured into individual file
per implementation. Some micro-optimizations were implemented
for some barriers (caching common computations in the barrier).
State subsription is now explicit with the TID counter allocated
on a per-barrier basis.
Tournament barriers remaining and then another round will be done
for correctness and algorithmic improvements.
These are the tournament and mcs barriers from "Algorithms for Scalable
Synchronization on Shared-Memory Multiprocessors." Validation tests have
also been added for these barriers to regressions/ck_barrier/validate.
This is the software combining tree barrier from the MCS paper. Currently,
it uses a binary tree; it may be changed later to use an n-ary tree.
Validation (combining_validation.c in regressions/ck_barrier/validate)
has also been added.
Instead of executing a join on the threads, aggregate existing state
of their counters. This can mean one missed increment per thread,
which is not a big deal.
Moved rdtsc and affinity logic to a single file which other
regression tests use. Single point of reference will ease
porting these to future architectures and platforms. Removed
invalid Copyright statement.
Added CK_CC_USED to force some code generation that I found
useful for debugging.
Added ck_stack latency tests and a modified version of djoseph's
modifications to benchmark.h for spinlock latency tests.
Samy Al Bahra
Samy Al Bahra
Samy Al Bahra
sbahra
David Joseph
Devon H. O'Dell