[BEAM-10630] Check load tests as part of the release process (#12455)

In the past, we have seen performance regressions in releases. We should make
sure that the release guide includes checking available performance
measurements.
diff --git a/website/www/site/content/en/contribute/release-guide.md b/website/www/site/content/en/contribute/release-guide.md
index 87eb732..8599b41 100644
--- a/website/www/site/content/en/contribute/release-guide.md
+++ b/website/www/site/content/en/contribute/release-guide.md
@@ -37,6 +37,9 @@
 
 1. Decide to release
 1. Prepare for the release
+1. Investigate performance regressions
+1. Create a release branch
+1. Verify release branch
 1. Build a release candidate
 1. Vote on the release candidate
 1. During vote process, run validation tests
@@ -45,7 +48,7 @@
 1. Promote the release
 
 
-### Decide to release
+## 1. Decide to release
 
 Deciding to release and selecting a Release Manager is the first step of the release process. This is a consensus-based decision of the entire community.
 
@@ -60,7 +63,7 @@
 
 **********
 
-## 1. Prepare for the release
+## 2. Prepare for the release
 
 Before your first release, you should perform one-time configuration steps. This will set up your security keys for signing the release and access to various release repositories.
 
@@ -244,7 +247,23 @@
 **********
 
 
-## 2. Create a release branch in apache/beam repository
+## 3. Investigate performance regressions
+
+Check the Beam load tests for possible performance regressions. Measurements are available on [metrics.beam.apache.org](http://metrics.beam.apache.org).
+
+All Runners which publish data should be checked for the following, in both *batch* and *streaming* mode:
+
+- [ParDo](http://metrics.beam.apache.org/d/MOi-kf3Zk/pardo-load-tests) and [GBK](http://metrics.beam.apache.org/d/UYZ-oJ3Zk/gbk-load-test): Runtime, latency, checkpoint duration
+- [Nexmark](http://metrics.beam.apache.org/d/ahuaA_zGz/nexmark): Query runtime for all queries
+- [IO](http://metrics.beam.apache.org/d/bnlHKP3Wz/java-io-it-tests-dataflow): Runtime
+
+If regressions are found, the release branch can still be created, but the regressions should be investigated and fixed as part of the release process.
+The role of the release manager is to file JIRA issues for each regression with the 'Fix Version' set to the to-be-released version. The release manager
+oversees these just like any other JIRA issue marked with the 'Fix Version' of the release. 
+
+The mailing list should be informed to allow fixing the regressions in the course of the release.
+
+## 4. Create a release branch in apache/beam repository
 
 Attention: Only committer has permission to create release branch in apache/beam.
 
@@ -367,7 +386,7 @@
 **********
 
 
-## 3. Verify release branch
+## 5. Verify release branch
 
 After the release branch is cut you need to make sure it builds and has no significant issues that would block the creation of the release candidate.
 There are 2 ways to perform this verification, either running automation script(recommended), or running all commands manually.
@@ -477,11 +496,16 @@
 
 * Description: Description of failure
 
+#### Inform the mailing list
+
+The dev@beam.apache.org mailing list should be informed about the release branch being cut. Alongside with this note,
+a list of pending issues and to-be-trigated issues should be included. Afterwards, this list can be refined and updated
+by the release manager and the Beam community.
 
 **********
 
 
-## 4. Triage release-blocking issues in JIRA
+## 6. Triage release-blocking issues in JIRA
 
 There could be outstanding release-blocking issues, which should be triaged before proceeding to build a release candidate. We track them by assigning a specific `Fix version` field even before the issue resolved.
 
@@ -528,7 +552,7 @@
 **********
 
 
-## 5. Build a release candidate
+## 7. Build a release candidate
 
 ### Checklist before proceeding
 
@@ -599,7 +623,7 @@
 **********
 
 
-## 6. Prepare documents
+## 8. Prepare documents
 
 ### Update and Verify Javadoc
 
@@ -748,7 +772,7 @@
 **********
 
 
-## 7. Vote and validate release candidate
+## 9. Vote and validate release candidate
 
 Once you have built and individually reviewed the release candidate, please share it for the community-wide review. Please review foundation-wide [voting guidelines](http://www.apache.org/foundation/voting.html) for more information.
 
@@ -1074,7 +1098,7 @@
 **********
 
 
-## 8. Finalize the release
+## 10. Finalize the release
 
 Once the release candidate has been reviewed and approved by the community, the release should be finalized. This involves the final deployment of the release candidate to the release repositories, merging of the website changes, etc.
 
@@ -1163,7 +1187,7 @@
 **********
 
 
-## 9. Promote the release
+## 11. Promote the release
 
 Once the release has been finalized, the last step of the process is to promote the release within the project and beyond.