From 401f9165174081efacc36f672b13058a7a16cf1a Mon Sep 17 00:00:00 2001
From: Christopher Baines <mail@cbaines.net>
Date: Tue, 8 Jul 2025 07:24:41 +0100
Subject: [PATCH] Tweak gc logging

---
 .../jobs/load-new-guix-revision.scm           | 65 ++++++++++++-------
 1 file changed, 40 insertions(+), 25 deletions(-)

diff --git a/guix-data-service/jobs/load-new-guix-revision.scm b/guix-data-service/jobs/load-new-guix-revision.scm
index 75be80e..4cbfd21 100644
--- a/guix-data-service/jobs/load-new-guix-revision.scm
+++ b/guix-data-service/jobs/load-new-guix-revision.scm
@@ -3406,10 +3406,46 @@ SKIP LOCKED")
        ;; instances have the data updated.
        (fix-derivation-output-details-hash-encoding conn)
 
-       (add-hook! after-gc-hook
-                  (lambda ()
-                    (simple-format (current-error-port)
-                                   "after gc\n")))
+       (spawn-fiber
+        (lambda ()
+          (let loop ((last-gc-times
+                      (or (assq-ref (gc-stats) 'times) 0))
+                     (last-gc-time-taken
+                      (assq-ref (gc-stats) 'gc-time-taken)))
+            (let* ((stats (gc-stats))
+                   (gc-times (or (assq-ref stats 'gc-times) 0))
+                   (gc-time-taken (assq-ref stats 'gc-time-taken)))
+              (when (> gc-times last-gc-times)
+                (let ((gc-time-taken
+                       (assq-ref stats 'gc-time-taken))
+                      (time-since-last
+                       (/ (- gc-time-taken
+                             last-gc-time-taken)
+                          internal-time-units-per-second))
+                      (gcs
+                       (- gc-times
+                          last-gc-times)))
+                  (format (current-error-port)
+                          "~d gc's (time taken: ~f, heap-allocated-since-gc: ~a MiB, heap size: ~a MiB, heap free: ~a MiB)\n"
+                          gcs
+                          (/ time-since-last
+                             gcs)
+                          (/ (assq-ref stats 'heap-allocated-since-gc)
+                             (expt 2. 20))
+                          (/ (assq-ref stats 'heap-size)
+                             (expt 2. 20))
+                          (/ (assq-ref stats 'heap-free-size)
+                             (expt 2. 20)))))
+
+              (when
+                  (perform-operation
+                   (choice-operation
+                    (wrap-operation (get-operation finished-channel)
+                                    (const #f))
+                    (wrap-operation (sleep-operation 3)
+                                    (const #t))))
+                (loop gc-times
+                      gc-time-taken))))))
 
        (with-exception-handler
            (lambda (exn)
@@ -3432,27 +3468,6 @@ SKIP LOCKED")
                (with-postgresql-transaction
                 conn
                 (lambda (conn)
-                  (spawn-fiber
-                   (lambda ()
-                     (while (perform-operation
-                             (choice-operation
-                              (wrap-operation (get-operation finished-channel)
-                                              (const #f))
-                              (wrap-operation (sleep-operation 20)
-                                              (const #t))))
-
-                       (let ((stats (gc-stats)))
-                         (simple-format
-                          (current-error-port)
-                          "process-job heap: ~a MiB used (~a MiB heap)~%"
-                          (round
-                           (/ (- (assoc-ref stats 'heap-size)
-                                 (assoc-ref stats 'heap-free-size))
-                              (expt 2. 20)))
-                          (round
-                           (/ (assoc-ref stats 'heap-size)
-                              (expt 2. 20))))))))
-
                   (match (select-job-for-update conn id)
                     (((id commit source git-repository-id))