gerrit01: some more tuning

* flip off proxy_buffering again
* enable REVWALK_USE_PRIORITY_QUEUE
* enable delta compression, because that's not a bottleneck and it's
  nicer on bandwidth

services/gerrit/default.nix

@@ -101,7 +101,7 @@ in
         core.packedGitMmap = true;
 
         ## Takes more CPU but the transfer is smaller.
-        pack.deltacompression = false;
+        pack.deltacompression = true;
         pack.threads = 8;
 
         # FIXME(raito):
@@ -218,6 +218,7 @@ in
         User = "git";
         Group = "git";
       };
+      environment.REVWALK_USE_PRIORITY_QUEUE = "true";
     };
   };
 }

services/gerrit/www.nix

@@ -25,7 +25,7 @@ in
             # The :443 suffix is a workaround for https://b.tvl.fyi/issues/88.
             proxy_set_header  Host $host:443;
             # Gerrit can throw a lot of data.
-            proxy_buffering on;
+            proxy_buffering off;
             # NGINX should not give up super fast. Things can take time.
             proxy_read_timeout 3600;
           }