noReadAhead option, CLOEXEC the LMDB file

TODO

@@ -28,4 +28,3 @@ rate limits (maybe not needed now that we have plugins?)
 
 misc
   ? periodic reaping of disconnected sockets (maybe autoping is doing this already)
-  ? why isn't the LMDB mapping CLOEXEC

golpe.yaml

@@ -115,6 +115,10 @@ config:
     desc: "Size of mmap() to use when loading LMDB (default is 10TB, does *not* correspond to disk-space used)"
     default: 10995116277760
     noReload: true
+  - name: dbParams__noReadAhead
+    desc: "Disables read-ahead when accessing the LMDB mapping. Reduces IO activity when DB size is larger than RAM."
+    default: false
+    noReload: true
 
   - name: events__maxEventSize
     desc: "Maximum size of normalised JSON, in bytes"

strfry.conf

@@ -11,6 +11,9 @@ dbParams {
 
     # Size of mmap() to use when loading LMDB (default is 10TB, does *not* correspond to disk-space used) (restart required)
     mapsize = 10995116277760
+
+    # Disables read-ahead when accessing the LMDB mapping. Reduces IO activity when DB size is larger than RAM. (restart required)
+    noReadAhead = true
 }
 
 events {