This CL gives the option to load classes lazily (on by default),
meaning that fields, procedures, constructors and redirecting
factory constructors of classes are not initially read,
but instead read when (or if) needed.
The idea being that many classes aren’t needed, and that
spending time on reading them is thus just a waste of time.
This is especially true in modular compilation where a lot
of modules needs to be given as input as the compilation at
hand might technically rely on it, but in practice only very
few of the classes are actually needed (or very few classes
actually need their members).
The below numbers are comparing a VM without this change and without
the lazy class hierarchy member lists change with
b31566b297 (the base change for those
two changes).
For running a simple hello-world script, on my machine 500 times
and doing statistics on it I can measure the following differences:
With verbose, from kernel_service startup to compile complete:
Difference at 95.0% confidence
-17.8 +/- 0.555817
-24.3455% +/- 0.760206%
(Student's t, pooled s = 4.48379)
With verbose, total runtime measure by `time`
Difference at 95.0% confidence
-19.346 +/- 0.905217
-12.0333% +/- 0.563051%
(Student's t, pooled s = 7.30242)
Without verbose, total runtime measure by `time`
Difference at 95.0% confidence
-17.862 +/- 0.842905
-12.0635% +/- 0.569276%
(Student's t, pooled s = 6.79974)
For running a number of modular compilations I’ve recorded an
improvement in actual runtime in the order of 20-37% depending
on the circumstance. In a real build system, though, the
difference seems to be more in the order of around 5%.
Change-Id: Id329bcf2b01d12c12d7a49f2b8abacd9c2447f05
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/115703
Commit-Queue: Jens Johansen <jensj@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Johnni Winther