Add some more triage follow-up info.

Author: nnethercote

triage/2020-07-21.md

@@ -2,12 +2,13 @@
 
 See the [README](README.md) for details on how this log was gathered.
 
-This week was a disaster, perf-wise. 28 revisions checked. At least 7
+This week was a disaster, perf-wise. 28 revisions checked. 7
 regressions, several of them ranging from large to huge, many in rollups. Some
 additional regressions may have occurred in rollups that were masked by other
 regressions/improvements. 3 improvements, one of which was a reversion of a
-regression. Unpicking all this is going to take days and I'm not confident
-we'll actually identify every regression. A follow-up thread on Zulip is
+regression. Thanks for Mark-Simulacrum and eddyb for follow-up measurements and
+adding new tooling to help investigate regressions in rollups. A follow-up
+thread on Zulip is
 [here](https://rust-lang.zulipchat.com/#narrow/stream/247081-t-compiler.2Fperformance/topic/Follow-up.20to.20the.20bad.20perf.20triage.20of.202020-07-21)
 
 In better news, rustdoc performance is now being benchmarked, thanks to the
@@ -20,12 +21,12 @@ Regressions
   ([instructions](https://perf.rust-lang.org/compare.html?start=39d5a61f2e4e237123837f5162cc275c2fd7e625&end=d3df8512d2c2afc6d2e7d8b5b951dd7f2ad77b02&stat=instructions:u)):
   Up to 73.0% losses on many benchmarks.
   [#74416](https://github.com/rust-lang/rust/pull/74416#issuecomment-660545238)
-  is at least partly at fault; it was reverted in
+  is at fault; it was reverted in
   [#74478](https://github.com/rust-lang/rust/pull/74478), see below.
 - [std: Switch from libbacktrace to gimli #73441](https://github.com/rust-lang/rust/pull/73441#issuecomment-660881380)
   ([instructions](https://perf.rust-lang.org/compare.html?start=7d31ffc1ac9e9ea356e896e63307168a64501b9d&end=1fa54ad9680cc82e7301f8ed4e9b7402dfd6ce0e&stat=instructions:u),
    [max-rss](https://perf.rust-lang.org/compare.html?start=7d31ffc1ac9e9ea356e896e63307168a64501b9d&end=1fa54ad9680cc82e7301f8ed4e9b7402dfd6ce0e&stat=max-rss)):
-  Up to 44.8% instruction increases on many benchmarks, and 5-10% max-rss increases on many benchmarks. I have requested it be reverted.
+  Up to 44.8% instruction increases on many benchmarks, and 5-10% max-rss increases on many benchmarks. Being reverted in [#74613](https://github.com/rust-lang/rust/pull/74613).
 - [Rollup of 11 pull requests #74468](https://github.com/rust-lang/rust/pull/74468#issuecomment-661371815)
   ([instructions](https://perf.rust-lang.org/compare.html?start=d3df8512d2c2afc6d2e7d8b5b951dd7f2ad77b02&end=7d31ffc1ac9e9ea356e896e63307168a64501b9d&stat=instructions:u)):
   Up to 10.2% losses on many benchmarks. [#74069](https://github.com/rust-lang/rust/pull/74069) [responsible](https://perf.rust-lang.org/compare.html?start=d3df8512d2c2afc6d2e7d8b5b951dd7f2ad77b02&end=cfade73820883adf654fe34fd6b0b03a99458a51), revert [posted](https://github.com/rust-lang/rust/pull/74611).