reload: turn off incremental QML garbage collection

After a 33-minute suspend the desktop shell sat at ~45% of a core: its
main thread ran flat out for about a second every two seconds, in step
with the Perf 2s timer. Stack samples were almost all QV4 GC
(GCStateMachine::transition, MarkStack::drain) entered from allocData via
tryForceGCCompletion, under the regex loop in Perf.vram(), a 177-line
parse that should take microseconds. The main thread also posted ~1000
events a second to its own eventfd, against a few dozen in the other
shells. Reading: Qt 6.11's incremental collector, the default since 6.8,
never completed a cycle after resume, so every allocation forced a full
mark.

QV4_GC_TIMELIMIT=0 is Qt's documented switch back to non-incremental
collection. With it, after a 31-minute suspend the shell stayed at 0.3%
and ~37 wakeups a second. The live autostart.lua sets it too; keep the
two in step.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/reload.sh b/reload.sh
index 243a132..e856e90 100755
--- a/reload.sh
+++ b/reload.sh
@@ -23,6 +23,12 @@ if [ $# -eq 0 ]; then
     set -- "${@%/shell.qml}"
 fi
 
+# Qt 6.8+ runs the QML garbage collector incrementally. After a suspend the
+# desktop shell's collector was seen stuck mid-cycle: every allocation forced a
+# full mark, a 177-line parse took a second, and a core stayed busy. 0 turns
+# incremental collection off; keep it in step with hypr autostart.lua.
+export QV4_GC_TIMELIMIT=0
+
 for c in "$@"; do
     c=${c%/}
     [ -f "$c/shell.qml" ] || { echo "$c: no shell.qml" >&2; continue; }