A high-concurrency transactional memory (TM) implementation needs to track
concurrent accesses, buffer speculative updates, and manage conflicts, 
requiring support for data isolation and memory monitoring (DIMM). 
In this talk, I will present a system we call 
FlexTM (FLEXible Transactional Memory), 
that utilizes four decoupled hardware mechanisms that provide DIMM support: read
and write signatures, which summarize per-thread access sets;
per-thread conflict summary tables (CSTs), which identify the
threads with which conflicts have occurred; Programmable Data
Isolation, which maintains speculative updates in the local
cache and employs a thread-private buffer (in virtual memory) in
the rare event of overflow; and Alert-On-Update, which
selectively notifies threads about coherence events.  
All mechanisms are software-accessible, to enable virtualization 
across context switches, overflow, and page swaps. 
FlexTM (1) decouples conflict detection from conflict management and allows 
software to control management time (i.e., eager or lazy);
(2) tracks conflicts on a thread-by-thread basis rather than a 
location-by-location basis and enables software to dictate policy 
without the overhead of separate metadata; and 
(3) permits TM components to be used for non-transactional purposes.
To the best of our knowledge, it is the first hardware TM to admit 
a distributed commit protocol with no global arbitration. 
If time permits, I will present results to demonstrate the efficiency of the system,  as well as the utility of its flexible policies. 
I will also demonstrate how the DIMM mechanisms may be 
used for other non-transactional purposes such as program debugging.