Merge #156997 #157005

156997: kvserver: run bench without extra arguments r=pav-kv a=stevendanna

Without these additions, users of `./dev bench` need to manually specify an explicit bazel target for the kvserver_test package. This always causes a few seconds (or minutes) of confusion because (1) most of us are used to not having to specify the test package and (2) its reasonable to first suspect your recent change when you hit some bazel error.

Informs #147833
Epic: None
Release note: none

157005: mmaprototype: explain why localities don't care about the keys r=wenyihu6 a=tbg

It's because operators must use matching keys across the cluster, so only the values can be different.

For example, it's not allowed to have one node with `region=foo` and another with `fruit=banana`. It must be `region=foo`,`region=banana` and that point the key no longer plays a role since it always matches.

Epic: CRDB-55052

Co-authored-by: Steven Danna <danna@cockroachlabs.com>
Co-authored-by: Tobias Grieger <tobias.b.grieger@gmail.com>

Author: 3 people

pkg/kv/kvserver/BUILD.bazel

@@ -616,9 +616,11 @@ go_proto_library(
     proto = ":kvserver_proto",
     visibility = ["//visibility:public"],
     deps = [
+        "//pkg/kv/kvpb",  # keep
         "//pkg/kv/kvserver/kvserverpb",
         "//pkg/roachpb",
         "//pkg/storage/enginepb",
+        "//pkg/util/uuid",  # keep
         "@com_github_gogo_protobuf//gogoproto",
     ],
 )

pkg/kv/kvserver/allocator/mmaprototype/constraint.go

@@ -1922,6 +1922,14 @@ func (lti *localityTierInterner) unintern(lt localityTiers) roachpb.Locality {
 	return locality
 }
 
+// localityTiers encodes a locality value hierarchy, represented by codes
+// from an associated stringInterner.
+//
+// Note that CockroachDB operators must use matching *keys*[1] across all nodes
+// in each deployment, so we only need to deal with a slice of locality
+// *values*.
+//
+// [1]: https://www.cockroachlabs.com/docs/stable/cockroach-start#locality
 type localityTiers struct {
 	tiers []stringCode
 	// str is useful as a map key for caching computations.