diff mercurial/localrepo.py @ 51108:0250e45040f1

revlog: add a small cache of unfiltered chunk

This can provides a massive boost to the reading of multiple revision and the
computation of a valid delta chain.

This greatly help operation like `hg log --patch`, delta computation (helping
pull/unbundle), linkrev adjustment (helping copy tracing).

A first round of benchmark for `hg log --patch --limit 1000` shows improvement
in the 10-20% range on "small" repository like pypy or mercurial and large
improvements (about 33%) for more complex ones like netbeans and mozilla's.

These speeds up are consistent with the improvement to `hg pull` (from a server
sending poor deltas) I saw benchmarking this last year. Further benchmark will
be run during the freeze.

I added some configuration in the experimental space to be able to further test
the effect of various tuning for now. This feature should fit well in the
"usage/resource profile" configuration that we should land next cycle.

When it does not provides a benefit the overhead of the cache seem to be around
2%, a small price for the big improvement. In addition I believe we could shave
most of this overhead with a more efficent lru implementation.

--- a/mercurial/localrepo.py	Fri Oct 27 02:57:09 2023 +0200
+++ b/mercurial/localrepo.py	Fri Oct 27 08:54:41 2023 +0200
@@ -1089,6 +1089,16 @@
     if chunkcachesize is not None:
         data_config.chunk_cache_size = chunkcachesize
 
+    if ui.configbool(b'experimental', b'revlog.uncompressed-cache.enabled'):
+        factor = ui.configint(
+            b'experimental', b'revlog.uncompressed-cache.factor'
+        )
+        count = ui.configint(
+            b'experimental', b'revlog.uncompressed-cache.count'
+        )
+        data_config.uncompressed_cache_factor = factor
+        data_config.uncompressed_cache_count = count
+
     delta_config.delta_both_parents = ui.configbool(
         b'storage', b'revlog.optimize-delta-parent-choice'
     )