diff --git a/src/librustc/ty/query/plumbing.rs b/src/librustc/ty/query/plumbing.rs
index c724209f87862..781ed03f22418 100644
--- a/src/librustc/ty/query/plumbing.rs
+++ b/src/librustc/ty/query/plumbing.rs
@@ -24,6 +24,8 @@ use std::hash::{Hash, Hasher};
 use std::mem;
 use std::num::NonZeroU32;
 use std::ptr;
+#[cfg(debug_assertions)]
+use std::sync::atomic::{AtomicUsize, Ordering};
 
 pub(crate) struct QueryStateShard<'tcx, D: QueryAccessors<'tcx> + ?Sized> {
     pub(super) cache: <<D as QueryAccessors<'tcx>>::Cache as QueryCache<D::Key, D::Value>>::Sharded,
@@ -51,7 +53,7 @@ pub(crate) struct QueryState<'tcx, D: QueryAccessors<'tcx> + ?Sized> {
     pub(super) cache: D::Cache,
     pub(super) shards: Sharded<QueryStateShard<'tcx, D>>,
     #[cfg(debug_assertions)]
-    pub(super) cache_hits: usize,
+    pub(super) cache_hits: AtomicUsize,
 }
 
 impl<'tcx, Q: QueryAccessors<'tcx>> QueryState<'tcx, Q> {
@@ -100,7 +102,7 @@ impl<'tcx, M: QueryAccessors<'tcx>> Default for QueryState<'tcx, M> {
             cache: M::Cache::default(),
             shards: Default::default(),
             #[cfg(debug_assertions)]
-            cache_hits: 0,
+            cache_hits: AtomicUsize::new(0),
         }
     }
 }
@@ -439,6 +441,10 @@ impl<'tcx> TyCtxt<'tcx> {
                 if unlikely!(self.prof.enabled()) {
                     self.prof.query_cache_hit(index.into());
                 }
+                #[cfg(debug_assertions)]
+                {
+                    state.cache_hits.fetch_add(1, Ordering::Relaxed);
+                }
                 on_hit(value, index)
             },
             on_miss,
diff --git a/src/librustc/ty/query/stats.rs b/src/librustc/ty/query/stats.rs
index cecad5f2eebd7..d257320d4eaf6 100644
--- a/src/librustc/ty/query/stats.rs
+++ b/src/librustc/ty/query/stats.rs
@@ -6,6 +6,8 @@ use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 
 use std::any::type_name;
 use std::mem;
+#[cfg(debug_assertions)]
+use std::sync::atomic::Ordering;
 
 trait KeyStats {
     fn key_stats(&self, stats: &mut QueryStats);
@@ -42,7 +44,7 @@ fn stats<'tcx, Q: QueryAccessors<'tcx>>(
     let mut stats = QueryStats {
         name,
         #[cfg(debug_assertions)]
-        cache_hits: map.cache_hits,
+        cache_hits: map.cache_hits.load(Ordering::Relaxed),
         #[cfg(not(debug_assertions))]
         cache_hits: 0,
         key_size: mem::size_of::<Q::Key>(),
@@ -108,8 +110,10 @@ pub fn print_stats(tcx: TyCtxt<'_>) {
         queries.iter().filter(|q| q.local_def_id_keys.is_some()).collect();
     def_id_density.sort_by_key(|q| q.local_def_id_keys.unwrap());
     println!("\nLocal DefId density:");
+    let total = tcx.hir().definitions().def_index_count() as f64;
     for q in def_id_density.iter().rev() {
-        println!("   {} - {}", q.name, q.local_def_id_keys.unwrap());
+        let local = q.local_def_id_keys.unwrap();
+        println!("   {} - {} = ({}%)", q.name, local, (local as f64 * 100.0) / total);
     }
 }