On Wed, Feb 08, 2023 at 12:07:20AM -0300, Leonardo Brás wrote: > Hello Paul, > > I have been reading the book, until I stumbled on Quick Quiz 3.7, > Table E.1: Performance of Synchronization Mechanisms > on 16-CPU 2.8 GHz Intel X5550 (Nehalem) System > > <Copying from source, since the PDF is a little tricky> > > The first part looks like: > > Clock period & 0.4 & 1.0 \\ > Same-CPU CAS & 12.2 & 33.8 \\ > Same-CPU lock & 25.6 & 71.2 \\ > Blind CAS & 12.9 & 35.8 \\ > CAS & 7.0 & 19.4 \\ > > In this case, what would be the last lines "Blind CAS" and "CAS" referring to ? > > (For a second I thought it could be "In-Core Blind CAS" and "In-Core CAS" like > in Table 3.1, but that would not make sense: This "CAS" is faster than the > previous "Same-CPU CAS". ) I was surprised myself, but those measurements are quite real. My best guess is that the two threads in the core are able to overlap their accesses, while the single CPU must do everything sequentially. Strange, but whatever the reason, true! ;-) Thanx, Paul
