Intel® Architecture Instruction Set Extensions Programming Reference

INTEL® ADVANCED VECTOR EXTENSIONS
Details of enumerating these instruction enhancements are described in detail in Section 2.2.4.
1.7 INTEL ® TRANSACTIONAL SYNCHRONIZATION EXTENSIONS
Multithreaded applications take advantage of increasing number of cores to achieve high performance. However,
writing multi-threaded applications requires programmers to implement various software mechanisms to handle
data sharing among multiple threads. Access to shared data typically requires synchronization mechanisms. These
mechanisms ensure multiple threads update shared data by serializing operations on the shared data, often
through the use of a critical section protected by a lock.
Since serialization limits concurrency, programmers try to limit synchronization overheads. They do this either
through minimizing the use of synchronization or through the use of fine-grain locks; where multiple locks protect
different shared data. Unfortunately, this process is difficult and error prone; a missed or incorrect synchronization
can cause an application to fail.
Conservatively adding synchronization and using coarser granularity locks, where a few locks each protect many
items of shared data, helps avoid correctness problems but limits performance due to excessive serialization. While
programmers must use static information to determine when to serialize, the determination as to whether to actually
serialize is best done dynamically.
Intel ® Transactional Synchronization Extensions (Intel ® TSX) allows the processor to determine dynamically
whether threads need to serialize through critical sections, and to perform serialization only when required. This
lets processors expose and exploit concurrency hidden in an application due to dynamically unnecessary synchronization.
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