Using MADV_FREE on Solaris/Illumos
diff --git a/configure.ac b/configure.ac
index 61fd868..a80c05d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -296,6 +296,7 @@
   *-*-solaris2*)
 	CFLAGS="$CFLAGS"
 	abi="elf"
+	AC_DEFINE([JEMALLOC_PURGE_MADVISE_FREE], [ ])
 	RPATH='-Wl,-R,$(1)'
 	dnl Solaris needs this for sigwait().
 	CPPFLAGS="$CPPFLAGS -D_POSIX_PTHREAD_SEMANTICS"