hurts the internal parallelism. MHL-M has high mapping
persistence overhead because it has to make the
mapping table persistent on each transaction commit.
Comparatively, LightTx supports arbitrary transaction
concurrency and achieves the highest performance and
nearly the lowest overhead in all evaluated aspects.
5 CONCLUSION
Providing flexible support for transactions at low overhead
is a key challenge in transactional SSD (TxSSD)
design. In this paper, we propose a novel TxSSD design,
called LightTx, to achieve high transaction flexibility at
low overhead. To improve transaction flexibility, LightTx
decouples concurrency control and transaction recovery
of transactions and manages them respectively in
software and hardware, by extending the transactional
interface of SSDs. Inside the SSD, LightTx reduces page
dependencies to improve concurrency using a pageindependent
commit protocol. To reduce transactional
overhead, LightTx introduces a zone-based transaction
state tracking scheme to track the recent updates, so
as to reduce the mapping persistence overhead while
providing fast recovery. The zone-based scheme also
retires the dead transactions to reduce the transaction
tracking overhead, including the overhead of garbage
collection and memory consumption. Evaluations show
that LightTx is an effective, efficient and flexible transactional
SSD design that achieves high performance at
low overhead.