"Smith, Barry F." <bsm...@mcs.anl.gov> writes: >> On Sep 21, 2019, at 11:43 PM, Jed Brown <j...@jedbrown.org> wrote: >> >> "Smith, Barry F." <bsm...@mcs.anl.gov> writes: >> >>> Jed, >>> >>> What does latency as a function of message size mean? It is in the plots >> >> It's just the wall-clock time to ping-pong a message of that size. All >> the small sizes take the same amount of time (i.e., the latency), then >> transition to being network bandwidth limited for large sizes. > > Thanks, this is fine for the small size. But he has the graph up to > size 1000000 and the plotted values change for larger sizes, surely > for 1000000 the time is a combination of latency and bandwidth? > Isn't calling it latency a misnomer, or do people use this > inconsistent terminology when doing ping-pongs?
Latency of an operation is just how long from when you initiate it until it completes. Latency in a performance model, such as LogP, is additive with other factors (like bandwidth and compute throughput).
