diff --git a/src/tools/rust-analyzer/crates/ide-db/src/prime_caches.rs b/src/tools/rust-analyzer/crates/ide-db/src/prime_caches.rs
index 1ca52060118a..b4486d150269 100644
--- a/src/tools/rust-analyzer/crates/ide-db/src/prime_caches.rs
+++ b/src/tools/rust-analyzer/crates/ide-db/src/prime_caches.rs
@@ -29,7 +29,7 @@ pub struct ParallelPrimeCachesProgress {
 
 pub fn parallel_prime_caches(
     db: &RootDatabase,
-    num_worker_threads: u8,
+    num_worker_threads: usize,
     cb: &(dyn Fn(ParallelPrimeCachesProgress) + Sync),
 ) {
     let _p = tracing::info_span!("parallel_prime_caches").entered();
diff --git a/src/tools/rust-analyzer/crates/ide/src/lib.rs b/src/tools/rust-analyzer/crates/ide/src/lib.rs
index e9408bf89766..a2ac62341df9 100644
--- a/src/tools/rust-analyzer/crates/ide/src/lib.rs
+++ b/src/tools/rust-analyzer/crates/ide/src/lib.rs
@@ -284,7 +284,7 @@ impl Analysis {
         })
     }
 
-    pub fn parallel_prime_caches<F>(&self, num_worker_threads: u8, cb: F) -> Cancellable<()>
+    pub fn parallel_prime_caches<F>(&self, num_worker_threads: usize, cb: F) -> Cancellable<()>
     where
         F: Fn(ParallelPrimeCachesProgress) + Sync + std::panic::UnwindSafe,
     {
diff --git a/src/tools/rust-analyzer/crates/rust-analyzer/src/config.rs b/src/tools/rust-analyzer/crates/rust-analyzer/src/config.rs
index 497fd67e92a7..98686f2cd53a 100644
--- a/src/tools/rust-analyzer/crates/rust-analyzer/src/config.rs
+++ b/src/tools/rust-analyzer/crates/rust-analyzer/src/config.rs
@@ -73,7 +73,7 @@ config_data! {
         /// Warm up caches on project load.
         cachePriming_enable: bool = true,
         /// How many worker threads to handle priming caches. The default `0` means to pick automatically.
-        cachePriming_numThreads: ParallelCachePrimingNumThreads = 0u8,
+        cachePriming_numThreads: NumThreads = NumThreads::Physical,
 
         /// Pass `--all-targets` to cargo invocation.
         cargo_allTargets: bool           = true,
@@ -583,7 +583,7 @@ config_data! {
         notifications_unindexedProject: bool      = false,
 
         /// How many worker threads in the main loop. The default `null` means to pick automatically.
-        numThreads: Option<usize> = None,
+        numThreads: Option<NumThreads> = None,
 
         /// Expand attribute macros. Requires `#rust-analyzer.procMacro.enable#` to be set.
         procMacro_attributes_enable: bool = true,
@@ -2095,15 +2095,22 @@ impl Config {
         }
     }
 
-    pub fn prime_caches_num_threads(&self) -> u8 {
-        match *self.cachePriming_numThreads() {
-            0 => num_cpus::get_physical().try_into().unwrap_or(u8::MAX),
-            n => n,
+    pub fn prime_caches_num_threads(&self) -> usize {
+        match self.cachePriming_numThreads() {
+            NumThreads::Concrete(0) | NumThreads::Physical => num_cpus::get_physical(),
+            &NumThreads::Concrete(n) => n,
+            NumThreads::Logical => num_cpus::get(),
         }
     }
 
     pub fn main_loop_num_threads(&self) -> usize {
-        self.numThreads().unwrap_or(num_cpus::get_physical())
+        match self.numThreads() {
+            Some(NumThreads::Concrete(0)) | None | Some(NumThreads::Physical) => {
+                num_cpus::get_physical()
+            }
+            &Some(NumThreads::Concrete(n)) => n,
+            Some(NumThreads::Logical) => num_cpus::get(),
+        }
     }
 
     pub fn typing_autoclose_angle(&self) -> bool {
@@ -2524,6 +2531,15 @@ pub enum TargetDirectory {
     Directory(Utf8PathBuf),
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq)]
+#[serde(rename_all = "snake_case")]
+#[serde(untagged)]
+pub enum NumThreads {
+    Physical,
+    Logical,
+    Concrete(usize),
+}
+
 macro_rules! _default_val {
     (@verbatim: $s:literal, $ty:ty) => {{
         let default_: $ty = serde_json::from_str(&$s).unwrap();
@@ -3260,6 +3276,24 @@ fn field_props(field: &str, ty: &str, doc: &[&str], default: &str) -> serde_json
                 },
             ],
         },
+        "Option<NumThreads>" => set! {
+            "anyOf": [
+                {
+                    "type": "null"
+                },
+                {
+                    "type": "number"
+                },
+                {
+                    "type": "string",
+                    "enum": ["physical", "logical", ],
+                    "enumDescriptions": [
+                        "Use the number of physical cores",
+                        "Use the number of logical cores",
+                    ],
+                },
+            ],
+        },
         _ => panic!("missing entry for {ty}: {default}"),
     }