compute_tools: enable passing through stripe size

compute_tools/src/config.rs

@@ -69,6 +69,17 @@ pub fn write_postgres_conf(
         )?;
     }
 
+    if let Some(stripe_size) = &spec.shard_stripe_size {
+        writeln!(
+            file,
+            "neon.stripe_size={}",
+            // TODO: postgres should take stripe size in page count, to match how the
+            // rest of the system stores it.
+            // https://github.com/neondatabase/neon/pull/5837#discussion_r1430485706
+            (stripe_size * 8 * 1024) / (1024 * 1024)
+        )?;
+    }
+
     match spec.mode {
         ComputeMode::Primary => {}
         ComputeMode::Static(lsn) => {

libs/compute_api/src/spec.rs

@@ -73,6 +73,9 @@ pub struct ComputeSpec {
 
     // information about available remote extensions
     pub remote_extensions: Option<RemoteExtSpec>,
+
+    // Stripe size for pageserver sharding, in pages
+    pub shard_stripe_size: Option<usize>,
 }
 
 /// Feature flag to signal `compute_ctl` to enable certain experimental functionality.