What does "Wall Duration" mean for?

[Hongbo Min]

Hi,

I found a new duration kind is added to chrome://tracing result view, it is called "Wall Duration". What does it stand for from cpu profiling perspective?

For example, the below is a example of ThreadProxy::BeginFrame tracing result:

Start 5179.077 ms

Wall Duration 17.242 ms

CPU Duration  8.361 ms

Self Time 0.061 ms

CPU Self Time 0.153 ms

The result shows the Wall Duration is 17.242ms, while CPU duration 8.361ms. 

Can we trust "Wall Duration" as the overhead of a code block traced?

Thanks...Hongbo

[Mike Frysinger]

it's short for "wall clock" as in "look at the clock on the wall to see how much time has passed" :)

-mike

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[Primiano Tucci]

Just for sake of clarity, note that CPU time is the active cpu time.

In other words if you have a piece of code like "x +=1; sleep(1)", the wall time will be 1+ε seconds, the cpu time will be ε (the time that it takes to do compute a sum)

In other words, the CPU time does not advance when your process is suspended (on a mutex, on I/O, on a sleep, etc).