Add SlowBots details for LUCI
diff --git a/SlowBots.md b/SlowBots.md
index 45e123c..7151557 100644
--- a/SlowBots.md
+++ b/SlowBots.md
@@ -1,15 +1,45 @@
# SlowBots
-The Go build system now supports "SlowBots", which are a way to configure the TryBots (pre-submit builders) to add additional builders into the set of build configurations that TryBots normally run.
+The Go build system supports "SlowBots", which are a way to configure the TryBots (pre-submit builders) to add additional builders into the set of build configurations that TryBots normally run.
-Normally TryBots only run things that are fast and elastically provisioned. That is, TryBots only run x86 things that run on Google Cloud where we have tons of capacity and can spin up many VMs at will, sharding out test execution widely so the TryBots complete in 5-10 minutes.
+Normally TryBots only run things that are fast and elastically provisioned. That is, TryBots run tests for ports that are available on Google Cloud where we have tons of capacity and can spin up many VMs at will, sharding out test execution widely so the TryBots complete in 5-10 minutes.
But sometimes that's not enough. SlowBots let you say that you're cool waiting a long time until some specific set of builders becomes available. (There is often only one physical machine for some configurations, and often backlogged with work, and that builder might be slow too.)
## Using SlowBots
-* Use the Gerrit web UI to reply and select `Run-TryBot` = `+1` as normal, but...
-* In the comment section (where it says _Say something nice..._), write a magic comment:
+Click "Choose Tryjobs" under the commit message and a dialog will appear.
+
+
+
+The dialog will ask you to click checkboxes for the builds you would like to run against your CL.
+
+
+
+Select the builds you would like to run, and click "Add". Each build's name roughly indicates what it will do, but below is some more detail:
+* Builds may start with `x_$REPO` where `$REPO` is some module like `golang.org/x/$REPO` (such as `x_review-gotip-linux-amd64`). This build will run tests in that repository.
+* If builds do not start with `x_$REPO` (like `gotip-linux-amd64`), they are testing the main Go repository (including the standard library and toolchain).
+* Builds will then always list a Go version to build against, like `gotip` or `go1.21`. The former builds against the `master` branch of the main Go repository, while the latter builds against the `HEAD` of the corresponding release branch.
+* Builds then list the OS and CPU architecture (specifically, the `GOOS` and `GOARCH`) to test against.
+* Lastly, builds list some modifications, such as `gotip-linux-amd64-longtest-race`. Below is a list of some of the modifications and what they mean:
+ * `longtest` runs the full suite of tests for the corresponding platform and repository.
+ * `race` runs tests under the race detector.
+ * `misccompile` will cross-compile all packages (including test packages) for all supported platforms as a smoke test. The platform for these builds is just the "host" platform for the cross-compilation.
+
+**There are currently a lot more possible builds listed than what's actually supported or valid.**
+
+Here are some general guidelines for which SlowBots will work as expected:
+* If you're running SlowBots for a CL for one of the `golang.org/x/$REPO` repositories, then all the `x_$REPO-.*` builders will work as expected. Other builds will fail.
+* If you're running SlowBots for a CL for the main Go repository, then every build that matches the branch the CL is for will work. For example, if you have a CL for the `master` branch, then every build with a name containing `gotip` will work as expected (`x_tools-gotip-linux-amd64`, `gotip-windows-amd64`, etc.). If you have a CL for the `release-branch.go1.21` branch, then every build with a name containing `go1.21` will work as expected (`x_tools-go1.21-linux-amd64`, `go1.21-windows-amd64`, etc.).
+
+TODO: Apply these guidelines as filters automatically.
+
+### Pre-LUCI SlowBots
+
+We're currently in the middle of a migration to a new open-source CI system created by the Chromium project called LUCI. The above instructions describe how to run SlowBots on LUCI, but not all ports have been migrated to LUCI yet. In the interim, these ports are still available on the old infrastructure. Below are instructions on how to use SlowBots on the old infrastructure.
+
+* Use the Gerrit web UI to reply and select `Run-TryBot` = `+1` instead of `Commit-Queue` = `+1`.
+* **Before clicking "Send"** write a magic comment in the comment section (where it says _Say something nice..._):
```
TRY=ppc64le, freebsd, netbsd-386, ios, linux-arm64-packet
@@ -29,7 +59,7 @@
When running TryBots again later, the most recent `TRY=` comment on the current patchset is used. To turn it off set `TRY=` with an empty string after the equals sign. If the current patchset doesn't have a `TRY=` comment, the most recent `TRY=` comment is used.
-## Pitfalls
+#### Pitfalls with Pre-LUCI SlowBots
* `TRY=` comments are ignored if they're not on the same comment that started the TryBots
* TryBots (and SlowBots) don't run if there's already a TryBot-Result
@@ -37,8 +67,4 @@
* If TryBots are already running, deleting the `Run-TryBot+1` vote and re-doing it won't re-start the TryBot set, so it won't look at your TRY= line, until the next run when it's done. (But you'll need to delete the TryBot-Result somehow: manually, rebasing, uploading new version)
* If you select a builder that's offline, it'll currently just wait forever for it to show up. There's no timeout yet.
* If you specify an unknown `TRY=` token, it'll just ignore it and won't report an error.
-* There's no `all` alias. That's kinda intentional, to prevent overuse that might cause the SlowBots to get even slower for everybody. But we might add it later anyway. See [golang.org/issue/34501#issuecomment-544585711](https://go.dev/issue/34501#issuecomment-544585711).
-
-## TODO
-
-The usability of SlowBots will be improved over time. It needs to report things better, make it easier to configure (both CLI and probably a web GUI picker UI), and support restarting things, or modifying in-progress TryBot runs to change the set of builders. Feedback welcome at [golang.org/issue/34501](https://go.dev/issue/34501).
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+* There's no `all` alias. That's kinda intentional, to prevent overuse that might cause the SlowBots to get even slower for everybody. But we might add it later anyway. See [golang.org/issue/34501#issuecomment-544585711](https://go.dev/issue/34501#issuecomment-544585711).
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