From 455d1f01d041baf58abc3c9baf5e59ee054d9c9b Mon Sep 17 00:00:00 2001 From: Eelco Dolstra Date: Tue, 12 Jun 2018 15:41:37 +0200 Subject: [PATCH] Don't scan for roots in dynamic libraries This reduces the risk of object liveness misdetection. For example, Glibc has an internal variable "mp_" that often points to a Boehm object, keeping it alive unnecessarily. Since we don't store any actual roots in global variables, we can just disable data segment scanning. With this, the max RSS doing 100 evaluations of nixos.tests.firefox.x86_64-linux.drvPath went from 718 MiB to 455 MiB. --- src/libexpr/eval.cc | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc index 1ab2b0ac1..113850bff 100644 --- a/src/libexpr/eval.cc +++ b/src/libexpr/eval.cc @@ -188,8 +188,15 @@ void initGC() #if HAVE_BOEHMGC /* Initialise the Boehm garbage collector. */ + + /* Don't look for interior pointers. This reduces the odds of + misdetection a bit. */ GC_set_all_interior_pointers(0); + /* We don't have any roots in data segments, so don't scan from + there. */ + GC_set_no_dls(1); + GC_INIT(); GC_set_oom_fn(oomHandler);