From dd188d3035e81cda94425d6e9287bcae63a2ac8d Mon Sep 17 00:00:00 2001
From: Samuel Dionne-Riel <samuel@dionne-riel.com>
Date: Fri, 21 Dec 2018 22:57:07 -0500
Subject: [PATCH] hydra-eval-jobs: Warn and resets maxHeapSize on bad values

This is because setting only the initial heap size to more than
the default value (or the configured value) will cause all initial evals
until maxHeapSize expands to the given value to abort.

The 1.1 multiplier comes from the the configured defaults on NixOS' hydra,
and from the previous multiplier used before
7876cf677ce086c22faf8909bcec7ac8811f1d39.
---
 src/hydra-eval-jobs/hydra-eval-jobs.cc | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/hydra-eval-jobs/hydra-eval-jobs.cc b/src/hydra-eval-jobs/hydra-eval-jobs.cc
index 2be3dd80..525f22c1 100644
--- a/src/hydra-eval-jobs/hydra-eval-jobs.cc
+++ b/src/hydra-eval-jobs/hydra-eval-jobs.cc
@@ -234,6 +234,18 @@ int main(int argc, char * * argv)
         initNix();
         initGC();
 
+        /* Read the current heap size, which is the initial heap size. */
+        GC_prof_stats_s gc;
+        GC_get_prof_stats(&gc, sizeof(gc));
+        auto initialHeapSizeInt = gc.heapsize_full;
+
+        /* Then make sure the maximum heap size will be bigger than the initial heap size. */
+        if (initialHeapSizeInt > maxHeapSize) {
+            printInfo("warning: evaluator_initial_heap_size (%d) bigger than evaluator_max_heap_size (%d).", initialHeapSizeInt, maxHeapSize);
+            maxHeapSize = initialHeapSizeInt * 1.1;
+            printInfo("         evaluator_max_heap_size now set to %d.", maxHeapSize);
+        }
+
         Path releaseExpr;
 
         struct MyArgs : LegacyArgs, MixEvalArgs