docs: Document system memory limit fallback feature in README.md

README.md

@@ -8,6 +8,14 @@ Automatically set `GOMEMLIMIT` to match Linux [cgroups(7)](https://man7.org/linu
 
 See more details about `GOMEMLIMIT` [here](https://tip.golang.org/doc/gc-guide#Memory_limit).
 
+## Notice
+
+Version `v0.5.0` introduces a fallback to system memory limits as an experimental feature when cgroup limits are unavailable. Activate this by setting `AUTOMEMLIMIT_EXPERIMENT=system`.
+You can also use system memory limits via `memlimit.FromSystem` provider directly.
+
+This feature is under evaluation and might become a default or be removed based on user feedback.
+If you have any feedback about this feature, please open an issue.
+
 ## Installation
 
 ```shell
@@ -36,6 +44,15 @@ func init() {
 		memlimit.WithRatio(0.9),
 		memlimit.WithProvider(memlimit.FromCgroup),
 	)
+	memlimit.SetGoMemLimitWithOpts(
+		memlimit.WithRatio(0.9),
+		memlimit.WithProvider(
+			memlimit.ApplyFallback(
+				memlimit.FromCgroup,
+				memlimit.FromSystem,
+			),
+		),
+	)
 	memlimit.SetGoMemLimitWithEnv()
 	memlimit.SetGoMemLimit(0.9)
 	memlimit.SetGoMemLimitWithProvider(memlimit.Limit(1024*1024), 0.9)