NB-FEB: An Easy-to-Use and Scalable Universal Synchronization Primitive for Parallel Programming
This paper addresses the problem of universal synchronization
primitives that can support scalable thread synchronization
for large-scale many-core architectures. The universal
synchronization primitives that have been deployed widely
in conventional architectures, are the compare-and-swap (CAS)
and load-linked/store-conditional (LL/SC) primitives. However,
such synchronization primitives are expected to reach
their scalability limits in the evolution to many-core architectures
with thousands of cores.
We introduce a non-blocking full/empty bit primitive, or
NB-FEB for short, as a promising synchronization primitive
for parallel programming on may-core architectures. We show
that the NB-FEB primitive is universal, scalable, feasible and
convenient to use. NB-FEB, together with registers, can solve
the consensus problem for an arbitrary number of processes
(universality). NB-FEB is combinable, namely its memory requests
to the same memory location can be combined into
only one memory request, which consequently mitigates performance
degradation due to synchronization "hot spots" (scalability).
Since NB-FEB is a variant of the original full/empty
bit that always returns a value instead of waiting for a conditional
flag, it is as feasible as the original full/empty bit, which
has been implemented in many computer systems (feasibility).
The original full/empty bit is well-known as a special-purpose
primitive for fast producer-consumer synchronization and has
been used extensively in the specific domain of applications.
In this paper, we show that NB-FEB can be deployed easily
as a general-purpose primitive. Using NB-FEB, we construct
a non-blocking software transactional memory system
called NBFEB-STM, which can be used to handle concurrent
threads conveniently. NBFEB-STM is space efficient:
the space complexity of each object updated by N concurrent
threads/transactions is Θ(N), the optimal.
software transactional memory