Utilize buildCache in a smarter way to prevent pathological disk I/O storms.

third_party/buildbot_8_4p1/buildbot/status/web/status_json.py

Index: third_party/buildbot_8_4p1/buildbot/status/web/status_json.py
diff --git a/third_party/buildbot_8_4p1/buildbot/status/web/status_json.py b/third_party/buildbot_8_4p1/buildbot/status/web/status_json.py
index c3579390f43626750fc88daec81598f4da89fedc..e7cd932d10a0f874175a8b03bd0a9e29436e2278 100644
--- a/third_party/buildbot_8_4p1/buildbot/status/web/status_json.py
+++ b/third_party/buildbot_8_4p1/buildbot/status/web/status_json.py
@@ -641,8 +641,11 @@ class SlaveJsonResource(JsonResource):
             if builderName not in buildercache:
                 buildercache.add(builderName)
                 builder_status = self.status.getBuilder(builderName)
-                for i in range(1, builder_status.buildCacheSize - 1):
-                    build_status = builder_status.getBuild(-i)
+
+                buildnums = range(-1, -(builder_status.buildCacheSize - 1), -1)
+                builds = builder_status.getBuilds(buildnums)
+
+                for build_status in builds:
                     if not build_status or not build_status.isFinished():
                         # If not finished, it will appear in runningBuilds.
                         break