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authorEelco Dolstra <edolstra@gmail.com>2018-06-12T13·41+0200
committerEelco Dolstra <edolstra@gmail.com>2018-06-12T15·49+0200
commit455d1f01d041baf58abc3c9baf5e59ee054d9c9b (patch)
treeda03a435d576dde767e38fe3d0b88291c66f5f32 /src
parent30964103dc31c32ccb69912fdd73474cd65447e9 (diff)
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.
Diffstat (limited to 'src')
-rw-r--r--src/libexpr/eval.cc7
1 files changed, 7 insertions, 0 deletions
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 1ab2b0ac188e..113850bff1f9 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);