better stats

crates/ra_ide_api/src/status.rs

@@ -1,3 +1,6 @@
+use std::fmt;
+
+use ra_syntax::AstNode;
 use ra_db::{
     SourceFileQuery,
     salsa::{Database, debug::DebugQueryTable},
@@ -6,10 +9,53 @@ use ra_db::{
 use crate::db::RootDatabase;
 
 pub(crate) fn status(db: &RootDatabase) -> String {
-    let n_parsed_files = db.query(SourceFileQuery).entries::<Vec<_>>().len();
+    let file_stats = {
+        let mut stats = FilesStats::default();
+        for entry in db.query(SourceFileQuery).entries::<Vec<_>>() {
+            stats.total += 1;
+            if let Some(value) = entry.value {
+                stats.retained += 1;
+                stats.retained_size = stats
+                    .retained_size
+                    .checked_add(value.syntax().memory_size_of_subtree())
+                    .unwrap();
+            }
+        }
+        stats
+    };
     let n_defs = {
         let interner: &hir::HirInterner = db.as_ref();
         interner.len()
     };
-    format!("#n_parsed_files {}\n#n_defs {}\n", n_parsed_files, n_defs)
+    format!("{}\nn_defs {}\n", file_stats, n_defs)
+}
+
+#[derive(Default)]
+struct FilesStats {
+    total: usize,
+    retained: usize,
+    retained_size: usize,
+}
+
+impl fmt::Display for FilesStats {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        let (size, suff) = human_bytes(self.retained_size);
+        write!(
+            fmt,
+            "{} parsed_files, {} ({}{}) retained",
+            self.total, self.retained, size, suff
+        )
+    }
+}
+
+fn human_bytes(bytes: usize) -> (usize, &'static str) {
+    if bytes < 4096 {
+        return (bytes, " bytes");
+    }
+    let kb = bytes / 1024;
+    if kb < 4096 {
+        return (kb, "kb");
+    }
+    let mb = kb / 1024;
+    (mb, "mb")
 }