perf: introduce more cache invalidation option in perf::tags

This will help us to assert the performance of different versions in more
diverse situations.

We introduce helper function in the tags module in case invalidating such cache
becomes different in the future.

contrib/perf.py

@@ -882,23 +882,72 b' def perfheads(ui, repo, **opts):'
     fm.end()
 
 
+def _default_clear_on_disk_tags_cache(repo):
+    from mercurial import tags
+
+    repo.cachevfs.tryunlink(tags._filename(repo))
+
+
+def _default_clear_on_disk_tags_fnodes_cache(repo):
+    from mercurial import tags
+
+    repo.cachevfs.tryunlink(tags._fnodescachefile)
+
+
 @command(
     b'perf::tags|perftags',
     formatteropts
     + [
         (b'', b'clear-revlogs', False, b'refresh changelog and manifest'),
+        (
+            b'',
+            b'clear-on-disk-cache',
+            False,
+            b'clear on disk tags cache (DESTRUCTIVE)',
+        ),
+        (
+            b'',
+            b'clear-fnode-cache',
+            False,
+            b'clear on disk file node cache (DESTRUCTIVE),',
+        ),
     ],
 )
 def perftags(ui, repo, **opts):
+    """Benchmark tags retrieval in various situation
+
+    The option marked as (DESTRUCTIVE) will alter the on-disk cache, possibly
+    altering performance after the command was run. However, it does not
+    destroy any stored data.
+    """
+    from mercurial import tags
+
     opts = _byteskwargs(opts)
     timer, fm = gettimer(ui, opts)
     repocleartagscache = repocleartagscachefunc(repo)
     clearrevlogs = opts[b'clear_revlogs']
+    clear_disk = opts[b'clear_on_disk_cache']
+    clear_fnode = opts[b'clear_fnode_cache']
+
+    clear_disk_fn = getattr(
+        tags,
+        "clear_cache_on_disk",
+        _default_clear_on_disk_tags_cache,
+    )
+    clear_fnodes_fn = getattr(
+        tags,
+        "clear_cache_fnodes",
+        _default_clear_on_disk_tags_fnodes_cache,
+    )
 
     def s():
         if clearrevlogs:
             clearchangelog(repo)
             clearfilecache(repo.unfiltered(), 'manifest')
+        if clear_disk:
+            clear_disk_fn(repo)
+        if clear_fnode:
+            clear_fnodes_fn(repo)
         repocleartagscache()
 
     def t():

mercurial/tags.py

@@ -910,3 +910,13 b' class hgtagsfnodescache:'
             )
         finally:
             lock.release()
+
+
+def clear_cache_on_disk(repo):
+    """function used by the perf extension to "tags" cache"""
+    repo.cachevfs.tryunlink(_filename(repo))
+
+
+def clear_cache_fnodes(repo):
+    """function used by the perf extension to clear "file node cache"""
+    repo.cachevfs.tryunlink(_filename(repo))

tests/test-contrib-perf.t

@@ -194,7 +194,7 b' perfstatus'
                  benchmark the full generation of a stream clone
    perf::stream-locked-section
                  benchmark the initial, repo-locked, section of a stream-clone
-   perf::tags    (no help text available)
+   perf::tags    Benchmark tags retrieval in various situation
    perf::templating
                  test the rendering time of a given template
    perf::unbundle