ISMM 2021
Tue 22 Jun 2021 PLDI
co-located with PLDI 2021

Hardware transactional memory (HTM) provides a simpler programming model than lock-based synchronization. However, the hardware has limits that mean that HTM transactions may suffer costly aborts due to hardware capacity. Understanding HTM capacity is therefore critical to utilizing HTM. Unfortunately, crucial implementation details are undisclosed. In practice HTM capacity can manifest in confounding ways. It is therefore unsurprising that the literature reports results that appear to be highly contradictory, reporting capacities that vary by nearly three orders of magnitude. We conduct an in-depth study into the causes of HTM capacity aborts using four generations of Intel’s Transactional Synchronization Extension (TSX). We identify the apparent contradictions among prior work and by extending their methodologies are able to shed new light on the likely causes of HTM capacity aborts. In doing so, we reconcile the apparent contradictions. We focus on how replacement policies and the status of the cache can affect HTM capacity.

One source of surprising behavior appears to be the cache replacement policies used by the processors we evaluated. Both invalidating the cache and warming it up with the transactional working set can significantly improve the read capacity of transactions across the microarchitectures we tested. A further complication is that a physically indexed LLC will typically yield only half the total LLC capacity. We found that methodological differences in the prior work led to different warm up states and thus to their apparently contradictory findings. This paper deepens our understanding of how the underlying implementation and cache behavior affect the apparent capacity of HTM. Our insights on how to improve the read capacity of transactions can be used to optimize HTM applications, particularly those with large read transactions, such as those used in optimistic parallelization.

Conference Day
Tue 22 Jun

Displayed time zone: Eastern Time (US & Canada) change

18:00 - 21:00
Session 4: Compacting/Indexing/Transactioning & ClosingISMM 2021 at ISMM
Chair(s): Timothy M. JonesUniversity of Cambridge, UK
Exploiting Intel Optane Persistent Memory for Full Text Search
ISMM 2021
Shoaib AkramAustralian National University
Pre-print File Attached
Understanding and Utilizing Hardware Transactional Memory Capacity
ISMM 2021
Zixian CaiAustralian National University, Steve BlackburnAustralian National University, Michael D. BondOhio State University, USA
Link to publication DOI Media Attached
Fusuma: Double-ended Threaded Compaction
ISMM 2021
Hiro OnozawaThe University of Electro-Communications, Tomoharu UgawaUniversity of Tokyo, Hideya IwasakiUniversity of Electro-Communications, Japan
Day closing
Closing Remarks
ISMM 2021
Tobias WrigstadUppsala University, Sweden, Zhenlin WangMichigan Technological University