notes-on-rustc-timing.txt

## Some non-debug timings

touch ../src/librustc_middle/lib.rs && time infer-remake.sh stage1
touch ../src/librustc_middle/lib.rs && time infer-remake.sh notidy nocheck stage1

> real	2m2.034s
> user	27m5.253s
> sys	12m0.467s

> real	2m1.797s
> user	27m9.395s
> sys	12m23.794s

> real	2m2.364s
> user	27m10.960s
> sys	12m22.676s

touch ../src/librustc_middle/lib.rs && time infer-remake.sh notidy nocheck keep0 stage1

> real	0m26.016s
> user	0m54.010s
> sys	0m8.177s

> real	0m26.037s
> user	0m54.090s
> sys	0m7.805s

> real	0m26.057s
> user	0m54.007s
> sys	0m8.078s

touch ../src/librustc_middle/mir/mod.rs && time infer-remake.sh notidy nocheck stage1

> real	2m2.450s
> user	27m4.326s
> sys	11m52.220s

> real	2m2.426s
> user	27m18.808s
> sys	12m8.729s

> real	2m2.872s
> user	27m12.354s
> sys	12m9.106s

touch ../src/librustc_middle/mir/mod.rs && time infer-remake.sh notidy nocheck keep0 stage1

> real	0m26.172s
> user	0m54.044s
> sys	0m8.158s

> real	0m26.219s
> user	0m54.282s
> sys	0m8.270s

So, the time is cut roughly in half. That's exciting.

* With non-debug build, rustc_middle is taking 14 seconds to build. (So running time is scaled by 7/10)

* Outliers (timings > 1sec):

time: 1.192; rss: 567MB	rustc_middle, expand_crate
time: 1.192; rss: 567MB	rustc_middle, macro_expand_crate
time: 1.784; rss: 611MB	rustc_middle, configure_and_expand
time: 1.083; rss: 1294MB	rustc_middle, misc_checking_3
time: 6.572; rss: 1888MB	rustc_middle, monomorphization_collector_graph_walk
time: 1.237; rss: 2016MB	rustc_middle, partition_and_assert_distinct_symbols
time: 9.027; rss: 2059MB	rustc_middle, codegen_crate
time: 14.109; rss: 1007MB		total for rustc_middle


## Some (debug) timings

Note that this is only touching files, not modifying them, so it is either near best case or unrealistic,
since in practice when you rebuild you make an edit, and I think the incremental system is going to hash
stuff so that it won't redo certain kinds of work.

 * Even so, rustc_middle is takikng 20 seconds to build.

 * Outliers (timings > 1sec):

    time: 1.629; rss: 595MB	rustc_middle, expand_crate
    time: 1.629; rss: 595MB	rustc_middle, macro_expand_crate
    time: 2.399; rss: 639MB	rustc_middle, configure_and_expand
    time: 1.494; rss: 1337MB	rustc_middle, misc_checking_3
    time: 9.219; rss: 1972MB	rustc_middle, monomorphization_collector_graph_walk
    time: 1.705; rss: 2142MB	rustc_middle, partition_and_assert_distinct_symbols
    time: 1.030; rss: 2299MB	rustc_middle, encode_query_results
    time: 1.185; rss: 2305MB	rustc_middle, incr_comp_serialize_result_cache
    time: 1.242; rss: 2172MB	rustc_middle, incr_comp_persist_result_cache
    time: 1.643; rss: 2172MB	rustc_middle, serialize_dep_graph
    time: 12.910; rss: 2172MB	rustc_middle, codegen_crate
    time: 20.043; rss: 1086MB		total for rustc_middle

 * Obvious culprits worth double-checking: monomorphization_collector_graph_walk and codegen_crate.

 * Also, I should redo this run on a pure (non-dbg) opt build.

```
touch ../src/librustc_middle/lib.rs && time infer-remake.sh stage1
touch ../src/librustc_middle/lib.rs && time infer-remake.sh notidy nocheck stage1

> real	4m28.023s
> user	39m10.793s
> sys	13m49.381s

> real	3m50.542s
> user	37m42.963s
> sys	13m43.560s

> real	3m51.870s
> user	37m32.821s
> sys	13m21.657s

touch ../src/librustc_middle/lib.rs && time infer-remake.sh notidy nocheck keep0 stage1

> real	0m58.036s
> user	1m31.849s
> sys	0m19.924s

> real	0m57.752s
> user	1m31.483s
> sys	0m19.983s

> real	0m57.754s
> user	1m31.963s
> sys	0m19.695s

touch ../src/librustc_middle/mir/mod.rs && time infer-remake.sh notidy nocheck stage1

> real	3m32.358s
> user	37m16.834s
> sys	13m32.609s

> real	3m33.000s
> user	37m9.659s
> sys	13m24.636s

> real	3m32.693s
> user	37m14.624s
> sys	13m26.652s

touch ../src/librustc_middle/mir/mod.rs && time infer-remake.sh notidy nocheck keep0 stage1

> real	0m58.144s
> user	1m32.703s
> sys	0m20.047s

> real	0m57.843s
> user	1m32.194s
> sys	0m20.141s

> real	0m58.265s
> user	1m32.319s
> sys	0m20.020s
```