Readme: Add some perf stats

Author: bbhtt

README.md

@@ -1,7 +1,8 @@
 ### git_evtag_py
 
 A Python implementation of [git-evtag](https://github.com/cgwalters/git-evtag/),
-inspired by the [upstream Python implementation](https://github.com/cgwalters/git-evtag/blob/7c58b2021a066f1e552deeb37431bc70b6215d62/src/git-evtag-compute-py) but more feature complete and faster.
+inspired by the [upstream Python implementation](https://github.com/cgwalters/git-evtag/blob/7c58b2021a066f1e552deeb37431bc70b6215d62/src/git-evtag-compute-py)
+but more feature complete and [faster](#performance).
 
 This can,
 
@@ -65,3 +66,47 @@ uv run ruff format
 uv run ruff check --fix --exit-non-zero-on-fix
 uv run mypy .
 ```
+
+### Performance
+
+On `torvalds/linux.git`, v6.15 tag:
+
+```sh
+# git_evtag_py
+
+/bin/time -p git evtag
+Git-EVTag-Py-v0-SHA512: e7e3045a3f5b8f9cc538cc37a56143918306282f7200b9c860703bc839e0a7f4c59f36313d34e6ae9b825c2f77081dfe8e2d5f50f70030271ea17161e2e2fe83
+real 14.19
+user 8.60
+sys 7.21
+
+# git-evtag-compute-py
+
+/bin/time -p git-evtag-compute-py HEAD
+# git-evtag comment: submodules=0 commits=1 (262) trees=5895 (3908050) blobs=88843 (1510695775)
+Git-EVTag-v0-SHA512: e7e3045a3f5b8f9cc538cc37a56143918306282f7200b9c860703bc839e0a7f4c59f36313d34e6ae9b825c2f77081dfe8e2d5f50f70030271ea17161e2e2fe83
+real 152.06
+user 46.40
+sys 111.18
+```
+
+On `mesa/mesa.git` at `mesa-25.0.0` tag:
+
+```sh
+# git_evtag_py
+
+/bin/time -p git evtag
+Git-EVTag-Py-v0-SHA512: b7a88cbca3c1257855404ab6f16b9efaf1e9b9304f46ad45a5d1a283808e40a96011e9321f0c6a8aacfe3a1be9c3cb971b9169ba21bd1d2ccfeb52041da0475b
+real 1.93
+user 1.02
+sys 1.06
+
+# git-evtag-compute-py
+
+/bin/time -p git-evtag-compute-py HEAD
+# git-evtag comment: submodules=0 commits=1 (252) trees=714 (510170) blobs=10970 (283895423)
+Git-EVTag-v0-SHA512: b7a88cbca3c1257855404ab6f16b9efaf1e9b9304f46ad45a5d1a283808e40a96011e9321f0c6a8aacfe3a1be9c3cb971b9169ba21bd1d2ccfeb52041da0475b
+real 18.55
+user 5.83
+sys 13.45
+```