Issue #9113 has been updated by Nobuyoshi Nakada.


"linux-gnu" in "target_os" is substituted by "linux", so your AS_CASE never match.
You should check for libjemalloc availability instead, I think.

~~~diff
diff --git a/configure.in b/configure.in
index cf317af..a9037d6 100644
--- a/configure.in
+++ b/configure.in
@@ -1170,6 +1170,17 @@ AS_IF([test "x$with_gmp" != xno],
    with_gmp="$ac_cv_lib_gmp___gmpz_init"
    AS_IF([test -z "$with_gmp"], [with_gmp=no])])
 
+dnl use jemalloc on GNU/Linux, assume non-GNU has a better malloc than glibc
+AC_ARG_WITH([jemalloc],
+  [AS_HELP_STRING([--with-jemalloc],
+    [use jemalloc allocator. Default is yes on GNU/Linux, no elsewhere])],
+  )
+AS_IF([test "x$with_jemalloc" != xno],[
+  AC_CHECK_LIB([jemalloc],[malloc_conf],
+    [LIBS="-ljemalloc $LIBS"],
+    [AS_IF([test "x$with_jemalloc" = xyes],
+      [AC_MSG_WARN([No jemalloc found, using system malloc])])])
+
 dnl check for large file stuff
 mv confdefs.h confdefs1.h
 : > confdefs.h
~~~


----------------------------------------
Feature #9113: Ship Ruby for Linux with jemalloc out-of-the-box
https://bugs.ruby-lang.org/issues/9113#change-46706

* Author: Sam Saffron
* Status: Feedback
* Priority: Normal
* Assignee: 
* Category: build
* Target version: 
----------------------------------------
libc's malloc is a problem, it fragments badly meaning forks share less memory and is slow compared to tcmalloc or jemalloc. 

both jemalloc and tcmalloc are heavily battle tested and stable. 

2 years ago redis picked up the jemalloc dependency see: http://oldblog.antirez.com/post/everything-about-redis-24.html 

To quote antirez:
``
But an allocator is a serious thing. Since we introduced the specially encoded data types Redis started suffering from fragmentation. We tried different things to fix the problem, but basically the Linux default allocator in glibc sucks really, really hard. 
``

--- 

I recently benched Discourse with tcmalloc / jemalloc and default and noticed 2 very important thing: 

median request time reduce by up to 10% (under both)
PSS (proportional share size) is reduced by 10% under jemalloc and 8% under tcmalloc.

We can always use LD_PRELOAD to yank these in, but my concern is that standard distributions are using a far from optimal memory allocator. It would be awesome if the build, out-of-the-box, just checked if it was on Linux  (eg: https://github.com/antirez/redis/blob/unstable/src/Makefile#L30-L34 ) and then used jemalloc instead. 

---Files--------------------------------
0001-configure.in-add-with-jemalloc-option.patch (1.29 KB)


-- 
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