A rebuild after touching components/profile/mem.rs now takes 48 seconds (and
only rebuilds `profile` and `servo`) which is much lower than it used to be.
In comparison, a rebuild after touching components/profile_traits/mem.rs takes
294 seconds and rebuilds many more crates.
This change also removes some unnecessary crate dependencies in `net` and
`net_traits`.
- Most of util::memory has been moved into profile::mem, though the
`SizeOf` trait and related things remain in util::memory. The
`SystemMemoryReporter` code is now in a submodule
profile::mem::system_reporter.
- util::time has been moved entirely into profile::time.
This changeset implements the beginnings of fine-grained measurement of
Servo's data structures.
- It adds a new `SizeOf` trait, which is used to measure the memory used
by heap data structures, and implements it for some std types: Box,
String, Option, Arc, Vec, and DList.
- It adds a new `MemoryReporter` trait which is used to report memory
measurements from other threads to the memory profiler. Reporters are
registered and unregistered with the memory profiler, and the memory
profiler makes measurement requests of reporters when necessary.
- It plumbs a MemoryProfilerChan through to the layout task so it can
register a memory reporter.
- It implements the `SizeOf` trait for `DisplayList` and associated
types, and adds a memory reporter that uses it.
The display list hits 14.77 MiB when viewing
tests/html/perf-rainbow.html, and 2.51 MiB when viewing the Guardians of
the Galaxy Wikipedia page from servo-static-suite. Example output:
0.29: display-list::http://www.reddit.com/
0.00: display-list::http://static.adzerk.net/reddit/ads.html?sr=-reddit.com,loggedout&bust2#http://www.reddit.com
0.00: display-list::http://www.reddit.com/static/createadframe.html
There are a number of FIXME comments indicating sub-optimal things. This
is a big enough change for now that doing them as follow-ups seems best.
