mymalloc: add notes on the malloc implementation

1 files changed, 13 insertions, 0 deletions

diff --git a/mymalloc.h b/mymalloc.h
index 7d94246..2e0517b 100644
--- a/mymalloc.h
+++ b/mymalloc.h
@@ -6,6 +6,19 @@
  * adds wait-free free(3) multi-threading support to avoid contention
  * with call_rcu.
 
+ * The wait-free free(3) implementation was proposed for inclusion into
+   glibc in 2018 and may eventually become part of glibc:
+   https://inbox.sourceware.org/libc-alpha/20180731084936.g4yw6wnvt677miti@dcvr/
+
+ * Arenas are thread-local and returned to a global pool upon thread
+   destruction.  This works well for processes with stable thread counts,
+   but wastes memory in processes with unstable thread counts.
+
+ * On Linux with O_TMPFILE support, all allocations are backed by
+   a temporary file (in TMPDIR).  This avoids OOM errors on
+   memory-constrained systems due to the higher-than-normal memory
+   usage of mwrap itself.
+
  * memalign-family support is ignored (and reimplemented in mwrap_core.h).
    dlmalloc's attempts to improve memory-efficiency is prone to fragmentation
    if memaligned-allocations are repeatedly freed and relalocated while