Print trees in the memory profiler's output.

[nnethercote]

Memory reports are much nicer to read when grouped into trees, which requires giving each report a path instead of a name.

Sample output:

Begin memory reports
|
|    2.51 MiB -- pages
|       2.51 MiB -- url(file:///home/njn/moz/servo/../servo-static-suite/wikipedia/Guardians%20of%20the%20Galaxy%20(film)%20-%20Wikipedia,%20the%20free%20encyclopedia.html)
|          2.51 MiB -- display-list
|
|  238.89 MiB -- resident-according-to-smaps
|     188.31 MiB -- anonymous (rw-p)
|      27.29 MiB -- /home/njn/moz/servo/components/servo/target/debug/servo (r-xp)
|       7.82 MiB -- other
|       6.65 MiB -- [heap] (rw-p)
|       3.55 MiB -- /usr/lib/x86_64-linux-gnu/dri/i965_dri.so (r-xp)
|       1.42 MiB -- /lib/x86_64-linux-gnu/libc-2.19.so (r-xp)
|       1.13 MiB -- /home/njn/moz/servo/components/servo/target/debug/servo (r--p)
|       0.74 MiB -- /usr/lib/x86_64-linux-gnu/libX11.so.6.3.0 (r-xp)
|       0.73 MiB -- /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.20 (r-xp)
|       0.65 MiB -- /lib/x86_64-linux-gnu/libm-2.19.so (r-xp)
|       0.60 MiB -- /lib/x86_64-linux-gnu/libglib-2.0.so.0.4200.1 (r-xp)
|
|   71.08 MiB -- jemalloc-heap-active
|   59.11 MiB -- jemalloc-heap-allocated
|  180.00 MiB -- jemalloc-heap-mapped
|  232.87 MiB -- resident
|   54.43 MiB -- system-heap-allocated
| 3130.11 MiB -- vsize
|
End memory reports

[highfive]

Warning

• These commits modify unsafe code. Please review it carefully!

[hoppipolla-critic-bot]

Critic review: https://critic.hoppipolla.co.uk/r/4310

This is an external review system which you may optionally use for the code review of your pull request.

In order to help critic track your changes, please do not make in-place history rewrites (e.g. via git rebase -i or git commit --amend) when updating this pull request.

[nnethercote]

r? @jdm

[nnethercote]

It just occurred to me that a path! macro could be used to make path formation nicer -- i.e. hide all the to_owned calls.

[huonw]

I believe this should be possible in safe code, by explicitly moving out of t before reassigning, e.g.:

let tmp = t;
t = &mut tmp.children[i];

cf.

• http://stackoverflow.com/questions/27083544/trouble-porting-c-code-to-rust
• http://www.reddit.com/r/rust/comments/2zm0kh/how_to_mutably_traverse_a_linked_list_efficiently/

[jdm]

Two nits; otherwise it looks fine.

[jdm]

r+

[bors-servo]

saw approval from jdm
at nnethercote@fe3e932

[bors-servo]

merging nnethercote/servo/treeify-reports = fe3e932 into auto

[bors-servo]

nnethercote/servo/treeify-reports = fe3e932 merged ok, testing candidate = bfb80f2

[bors-servo]

all tests pass:
success: http://build.servo.org/builders/linux1/builds/1118
success: http://build.servo.org/builders/linux2/builds/1118
success: http://build.servo.org/builders/android/builds/1152
success: http://build.servo.org/builders/mac1/builds/1331
success: http://build.servo.org/builders/mac2/builds/1334
success: http://build.servo.org/builders/gonk/builds/300

[bors-servo]

fast-forwarding master to auto = bfb80f2