Update perfbot sheriffing docs.

tools/perf/docs/perf_bot_sheriffing.md

Index: tools/perf/docs/perf_bot_sheriffing.md
diff --git a/tools/perf/docs/perf_bot_sheriffing.md b/tools/perf/docs/perf_bot_sheriffing.md
index 702c93ca4cb9f71f1d56a7034cedb4d8209ae6a1..15be093b19b9427590b6dbe42c6df8679bd13356 100644
--- a/tools/perf/docs/perf_bot_sheriffing.md
+++ b/tools/perf/docs/perf_bot_sheriffing.md
@@ -38,10 +38,18 @@ Note that there are three different views:
         "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)**
@@ -72,6 +80,12 @@ 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.
 
+The chrome infrastructure team also maintains a dashboard you can use to view
+some debugging information about down machines. This is available at
+[go/chrome-infra-mon](http://go/chrome-infra-mon). To debug offline buildslaves,

[Sergey Berezin, 2016/09/29 18:23:01]

nit: this is the first time I see that go/ link :-) We have too many for the
same page (go/chrome-infra-viceroy, go/chrome-infra-graphs, ...).

Let's standardize on vi/chrome_infra.

[martiniss, 2016/09/29 20:07:14]

Done.

+you can look at the "Individual machine" dashboard, under the "Machines"

[Sergey Berezin, 2016/09/29 18:23:01]

nit: provide direct link, e.g. vi/chrome_infra/Machines/per_machine . In fact,
this link can go instead of the top-level link above (the top-level page is not
very helpful for this paragraph).

Another potentially interesting page is vi/chrome_infra/Buildbot/per_pool .
Searching for 'perf' gives a list of relevant slave pools like this one:

http://vi/chrome_infra/Buildbot/per_pool?pool=master.chromium.perf%3ALinux+Bu...

The top graph shows the number of configured and connected slaves + the load on
the pool.

[martiniss, 2016/09/29 20:08:35]

Done
I don't think this is very useful for perf sheriffs. sullivan@, do you think it
would be? My impression was that there isn't a big pool of machines that perf
needs to monitor, which is what that page is good for. I didn't include a link
to that.=

+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