Update perfbot sheriffing docs.

tools/perf/docs/perf_bot_sheriffing.md

 # Perf Bot Sheriffing
 
 The perf bot sheriff is responsible for keeping the bots on the chromium.perf
 waterfall up and running, and triaging performance test failures and flakes.
 
 **[Rotation calendar](https://calendar.google.com/calendar/embed?src=google.com_2fpmo740pd1unrui9d7cgpbg2k%40group.calendar.google.com)**
 
 ## Key Responsibilities
 
 *   [Handle Device and Bot Failures](#botfailures)
@@ skipping 20 matching lines @@
     it easier to see a summary.
 2.  [Waterfall view](https://uberchromegw.corp.google.com/i/chromium.perf/waterfall)
     shows more details, including recent changes.
 3.  [Firefighter](https://chromiumperfstats.appspot.com/) shows traces of
     recent builds. It takes url parameter arguments:
     *   **master** can be chromium.perf, tryserver.chromium.perf
     *   **builder** can be a builder or tester name, like
         "Android Nexus5 Perf (2)"
     *   **start_time** is seconds since the epoch.
 
+
+There is also [milo](https://luci-milo.appspot.com), which has the same data as
+buildbot, but mirrored in a different datastore. It is generally faster than
+buildbot, and links to it will not break, as the data is kept around for much
+longer.
+
 In addition to watching the waterfall directly,
 [Sheriff-O-Matic](https://sheriff-o-matic.appspot.com/chromium.perf) may
 optionally be used to easily track the different issues and associate
-them with specific bugs.
+them with specific bugs. It also attempts to group together similar failures
+across different builders, so it can help to see a higher level perspective on
+what is happening on the perf waterfall.
 
 You can see a list of all previously filed bugs using the
 **[Performance-Sheriff-BotHealth](https://bugs.chromium.org/p/chromium/issues/list?can=2&q=label%3APerformance-Sheriff-BotHealth)**
 label in crbug.
 
 Please also check the recent
 **[perf-sheriffs@chromium.org](https://groups.google.com/a/chromium.org/forum/#!forum/perf-sheriffs)**
 postings for important announcements about bot turndowns and other known issues.
 
 ## Handle Device and Bot Failures
 
 ### Offline Buildslaves
 
 Some build configurations, in particular the perf builders and trybots, have
 multiple machines attached. If one or more of the machines go down, there are
 still other machines running, so the console or waterfall view will still show
 green, but those configs will run at reduced throughput. At least once during
 your shift, you should check the lists of buildslaves and ensure they're all
 running.
 
 *   [chromium.perf buildslaves](https://build.chromium.org/p/chromium.perf/buildslaves)
 *   [tryserver.chromium.perf buildslaves](https://build.chromium.org/p/tryserver.chromium.perf/buildslaves)
 
 The machines restart between test runs, so just looking for "Status: Not
 connected" is not enough to indicate a problem. For each disconnected machine,
 you can also check the "Last heard from" column to ensure that it's been gone
 for at least an hour. To get it running again,
 [file a bug](https://bugs.chromium.org/p/chromium/issues/entry?labels=Pri-1,Performance-Sheriff-BotHealth,Infra-Troopers,OS-?&comment=Hostname:&summary=Buildslave+offline+on+chromium.perf)
-against the current trooper and read [go/bug-a-trooper](http://go/bug-a-trooper) for contacting troopers.
+against the current trooper and read [go/bug-a-trooper](http://go/bug-a-trooper)
+for contacting troopers.
+
+The chrome infrastructure team also maintains a set of dashboards you can use to
+view some debugging information about our systems. This is available at
+[vi/chrome_infra](http://vi/chrome_infra). To debug offline buildslaves,
+you can look at the "Individual machine" dashboard, (at
+[vi/chrome_infra/Machines/per_machine](http://vi/chrome_infra/Machines/per_machine)
+under the "Machines" section, which can show some useful information about the
+machine in question.
 
 ### Purple bots
 
 When a bot goes purple, it's usually because of an infrastructure failure
 outside of the tests. But you should first check the logs of a purple bot to
 try to better understand the problem. Sometimes a telemetry test failure can
 turn the bot purple, for example.
 
 If the bot goes purple and you believe it's an infrastructure issue, file a bug
 with
@@ skipping 176 matching lines @@
 
 **[Pri-2 bugs](https://bugs.chromium.org/p/chromium/issues/list?can=2&q=label%3APerformance-Sheriff-BotHealth+label%3APri-2)**
 are for disabled tests. These should be pinged weekly, and work towards fixing
 should be ongoing when the sheriff is not working on a Pri-1 issue. Here is the
 [list of Pri-2 bugs that have not been pinged in a week](https://bugs.chromium.org/p/chromium/issues/list?can=2&q=label:Performance-Sheriff-BotHealth%20label:Pri-2%20modified-before:today-7&sort=modified).
 
 <!-- Unresolved issues:
 1. Do perf sheriffs watch the bisect waterfall?
 2. Do perf sheriffs watch the internal clank waterfall?
 -->