From 11c73b36ac745d3fc0d309ac6884a71b8baef574 Mon Sep 17 00:00:00 2001
From: Rod S <rsheeter@google.com>
Date: Fri, 10 Nov 2023 09:22:17 -0800
Subject: [PATCH] Directly interfere to start kern sooner

---
 fontc/src/workload.rs | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/fontc/src/workload.rs b/fontc/src/workload.rs
index f47d5fad..65163598 100644
--- a/fontc/src/workload.rs
+++ b/fontc/src/workload.rs
@@ -232,11 +232,15 @@ impl<'a> Workload<'a> {
             .queued()
             .run();
 
-        let launchable: Vec<_> = self
+        let mut has_kern = false;
+        let mut launchable: Vec<_> = self
             .jobs_pending
             .iter()
             .filter_map(|(id, job)| {
                 if !job.running && self.can_run(job) {
+                    if matches!(id, AnyWorkId::Fe(FeWorkIdentifier::Kerning)) {
+                        has_kern = true;
+                    }
                     Some(id.clone())
                 } else {
                     None
@@ -245,6 +249,15 @@ impl<'a> Workload<'a> {
             .collect();
         trace!("Launchable: {launchable:?}");
 
+        // https://github.com/googlefonts/fontc/issues/456: try to avoid kern as long pole
+        if has_kern {
+            let kern_idx = launchable
+                .iter()
+                .position(|id| matches!(id, AnyWorkId::Fe(FeWorkIdentifier::Kerning)))
+                .unwrap();
+            launchable.swap(0, kern_idx);
+        }
+
         self.timer.add(timing.complete());
         launchable
     }