13 files changed, 72 insertions, 73 deletions
diff --git a/INSTALL b/INSTALL
index 55c919a..07f51d1 100644
--- a/INSTALL
+++ b/INSTALL
@@ -145,10 +145,6 @@ any of the following arguments (not a definitive list) to 'configure':
     memory allocation algorithm that causes semi-permanent VM map holes under
     normal jemalloc operation.
 
---enable-dss
-    Enable support for page allocation/deallocation via sbrk(2), in addition to
-    mmap(2).
-
 --disable-fill
     Disable support for junk/zero filling of memory, quarantine, and redzones.
     See the "opt.junk", "opt.zero", "opt.quarantine", and "opt.redzone" option
diff --git a/configure.ac b/configure.ac
index b47d572..dc817e1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -836,34 +836,22 @@ if test "x$enable_munmap" = "x1" ; then
 fi
 AC_SUBST([enable_munmap])
 
-dnl Do not enable allocation from DSS by default.
-AC_ARG_ENABLE([dss],
-  [AS_HELP_STRING([--enable-dss], [Enable allocation from DSS])],
-[if test "x$enable_dss" = "xno" ; then
-  enable_dss="0"
-else
-  enable_dss="1"
-fi
-],
-[enable_dss="0"]
-)
+dnl Enable allocation from DSS if supported by the OS.
+have_dss="1"
 dnl Check whether the BSD/SUSv1 sbrk() exists.  If not, disable DSS support.
 AC_CHECK_FUNC([sbrk], [have_sbrk="1"], [have_sbrk="0"])
 if test "x$have_sbrk" = "x1" ; then
   if test "x$sbrk_deprecated" == "x1" ; then
     AC_MSG_RESULT([Disabling dss allocation because sbrk is deprecated])
-    enable_dss="0"
-  else
-    AC_DEFINE([JEMALLOC_HAVE_SBRK], [ ])
+    have_dss="0"
   fi
 else
-  enable_dss="0"
+  have_dss="0"
 fi
 
-if test "x$enable_dss" = "x1" ; then
+if test "x$have_dss" = "x1" ; then
   AC_DEFINE([JEMALLOC_DSS], [ ])
 fi
-AC_SUBST([enable_dss])
 
 dnl Support the junk/zero filling option by default.
 AC_ARG_ENABLE([fill],
@@ -1461,7 +1449,6 @@ AC_MSG_RESULT([valgrind           : ${enable_valgrind}])
 AC_MSG_RESULT([xmalloc            : ${enable_xmalloc}])
 AC_MSG_RESULT([mremap             : ${enable_mremap}])
 AC_MSG_RESULT([munmap             : ${enable_munmap}])
-AC_MSG_RESULT([dss                : ${enable_dss}])
 AC_MSG_RESULT([lazy_lock          : ${enable_lazy_lock}])
 AC_MSG_RESULT([tls                : ${enable_tls}])
 AC_MSG_RESULT([===============================================================================])
diff --git a/doc/jemalloc.xml.in b/doc/jemalloc.xml.in
index 4acb07f..16dd0bb 100644
--- a/doc/jemalloc.xml.in
+++ b/doc/jemalloc.xml.in
@@ -448,8 +448,10 @@ for (i = 0; i < nbins; i++) {
     <manvolnum>2</manvolnum></citerefentry> to obtain memory, which is
     suboptimal for several reasons, including race conditions, increased
     fragmentation, and artificial limitations on maximum usable memory.  If
-    <option>--enable-dss</option> is specified during configuration, this
-    allocator uses both <citerefentry><refentrytitle>mmap</refentrytitle>
+    <citerefentry><refentrytitle>sbrk</refentrytitle>
+    <manvolnum>2</manvolnum></citerefentry> is supported by the operating
+    system, this allocator uses both
+    <citerefentry><refentrytitle>mmap</refentrytitle>
     <manvolnum>2</manvolnum></citerefentry> and
     <citerefentry><refentrytitle>sbrk</refentrytitle>
     <manvolnum>2</manvolnum></citerefentry>, in that order of preference;
@@ -625,16 +627,6 @@ for (i = 0; i < nbins; i++) {
         build configuration.</para></listitem>
       </varlistentry>
 
-      <varlistentry id="config.dss">
-        <term>
-          <mallctl>config.dss</mallctl>
-          (<type>bool</type>)
-          <literal>r-</literal>
-        </term>
-        <listitem><para><option>--enable-dss</option> was specified during
-        build configuration.</para></listitem>
-      </varlistentry>
-
       <varlistentry id="config.fill">
         <term>
           <mallctl>config.fill</mallctl>
@@ -790,10 +782,15 @@ for (i = 0; i < nbins; i++) {
         <manvolnum>2</manvolnum></citerefentry>) allocation precedence as
         related to <citerefentry><refentrytitle>mmap</refentrytitle>
         <manvolnum>2</manvolnum></citerefentry> allocation.  The following
-        settings are supported: &ldquo;disabled&rdquo;, &ldquo;primary&rdquo;,
-        and &ldquo;secondary&rdquo;.  The default is &ldquo;secondary&rdquo; if
-        <link linkend="config.dss"><mallctl>config.dss</mallctl></link> is
-        true, &ldquo;disabled&rdquo; otherwise.
+        settings are supported if
+        <citerefentry><refentrytitle>sbrk</refentrytitle>
+        <manvolnum>2</manvolnum></citerefentry> is supported by the operating
+        system: &ldquo;disabled&rdquo;, &ldquo;primary&rdquo;, and
+        &ldquo;secondary&rdquo;; otherwise only &ldquo;disabled&rdquo; is
+        supported.  The default is &ldquo;secondary&rdquo; if
+        <citerefentry><refentrytitle>sbrk</refentrytitle>
+        <manvolnum>2</manvolnum></citerefentry> is supported by the operating
+        system; &ldquo;disabled&rdquo; otherwise.
         </para></listitem>
       </varlistentry>
 
diff --git a/include/jemalloc/internal/arena.h b/include/jemalloc/internal/arena.h
index 0e14c2c..6de312e 100644
--- a/include/jemalloc/internal/arena.h
+++ b/include/jemalloc/internal/arena.h
@@ -434,7 +434,7 @@ void	*arena_ralloc(arena_t *arena, void *ptr, size_t oldsize, size_t size,
     size_t extra, size_t alignment, bool zero, bool try_tcache_alloc,
     bool try_tcache_dalloc);
 dss_prec_t	arena_dss_prec_get(arena_t *arena);
-void	arena_dss_prec_set(arena_t *arena, dss_prec_t dss_prec);
+bool	arena_dss_prec_set(arena_t *arena, dss_prec_t dss_prec);
 void	arena_stats_merge(arena_t *arena, const char **dss, size_t *nactive,
     size_t *ndirty, arena_stats_t *astats, malloc_bin_stats_t *bstats,
     malloc_large_stats_t *lstats);
diff --git a/include/jemalloc/internal/jemalloc_internal.h.in b/include/jemalloc/internal/jemalloc_internal.h.in
index a374e2a..4821b9b 100644
--- a/include/jemalloc/internal/jemalloc_internal.h.in
+++ b/include/jemalloc/internal/jemalloc_internal.h.in
@@ -85,7 +85,7 @@ static const bool config_debug =
     false
 #endif
     ;
-static const bool config_dss =
+static const bool have_dss =
 #ifdef JEMALLOC_DSS
     true
 #else
diff --git a/include/jemalloc/internal/jemalloc_internal_defs.h.in b/include/jemalloc/internal/jemalloc_internal_defs.h.in
index c166fbd..fc95967 100644
--- a/include/jemalloc/internal/jemalloc_internal_defs.h.in
+++ b/include/jemalloc/internal/jemalloc_internal_defs.h.in
@@ -76,9 +76,6 @@
  */
 #undef JEMALLOC_MUTEX_INIT_CB
 
-/* Defined if sbrk() is supported. */
-#undef JEMALLOC_HAVE_SBRK
-
 /* Non-empty if the tls_model attribute is supported. */
 #undef JEMALLOC_TLS_MODEL
 
diff --git a/src/arena.c b/src/arena.c
index d574100..8aa36fd 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -2243,13 +2243,16 @@ arena_dss_prec_get(arena_t *arena)
 	return (ret);
 }
 
-void
+bool
 arena_dss_prec_set(arena_t *arena, dss_prec_t dss_prec)
 {
 
+	if (have_dss == false)
+		return (dss_prec != dss_prec_disabled);
 	malloc_mutex_lock(&arena->lock);
 	arena->dss_prec = dss_prec;
 	malloc_mutex_unlock(&arena->lock);
+	return (false);
 }
 
 void
diff --git a/src/chunk.c b/src/chunk.c
index 90ab116..fdd693e 100644
--- a/src/chunk.c
+++ b/src/chunk.c
@@ -153,7 +153,7 @@ chunk_alloc(size_t size, size_t alignment, bool base, bool *zero,
 	assert((alignment & chunksize_mask) == 0);
 
 	/* "primary" dss. */
-	if (config_dss && dss_prec == dss_prec_primary) {
+	if (have_dss && dss_prec == dss_prec_primary) {
 		if ((ret = chunk_recycle(&chunks_szad_dss, &chunks_ad_dss, size,
 		    alignment, base, zero)) != NULL)
 			goto label_return;
@@ -167,7 +167,7 @@ chunk_alloc(size_t size, size_t alignment, bool base, bool *zero,
 	if ((ret = chunk_alloc_mmap(size, alignment, zero)) != NULL)
 		goto label_return;
 	/* "secondary" dss. */
-	if (config_dss && dss_prec == dss_prec_secondary) {
+	if (have_dss && dss_prec == dss_prec_secondary) {
 		if ((ret = chunk_recycle(&chunks_szad_dss, &chunks_ad_dss, size,
 		    alignment, base, zero)) != NULL)
 			goto label_return;
@@ -305,7 +305,7 @@ chunk_unmap(void *chunk, size_t size)
 	assert(size != 0);
 	assert((size & chunksize_mask) == 0);
 
-	if (config_dss && chunk_in_dss(chunk))
+	if (have_dss && chunk_in_dss(chunk))
 		chunk_record(&chunks_szad_dss, &chunks_ad_dss, chunk, size);
 	else if (chunk_dealloc_mmap(chunk, size))
 		chunk_record(&chunks_szad_mmap, &chunks_ad_mmap, chunk, size);
@@ -348,7 +348,7 @@ chunk_boot(void)
 			return (true);
 		memset(&stats_chunks, 0, sizeof(chunk_stats_t));
 	}
-	if (config_dss && chunk_dss_boot())
+	if (have_dss && chunk_dss_boot())
 		return (true);
 	extent_tree_szad_new(&chunks_szad_mmap);
 	extent_tree_ad_new(&chunks_ad_mmap);
diff --git a/src/chunk_dss.c b/src/chunk_dss.c
index 510bb8b..36133f1 100644
--- a/src/chunk_dss.c
+++ b/src/chunk_dss.c
@@ -32,7 +32,7 @@ static void *
 chunk_dss_sbrk(intptr_t increment)
 {
 
-#ifdef JEMALLOC_HAVE_SBRK
+#ifdef JEMALLOC_DSS
 	return (sbrk(increment));
 #else
 	not_implemented();
@@ -45,7 +45,7 @@ chunk_dss_prec_get(void)
 {
 	dss_prec_t ret;
 
-	if (config_dss == false)
+	if (have_dss == false)
 		return (dss_prec_disabled);
 	malloc_mutex_lock(&dss_mtx);
 	ret = dss_prec_default;
@@ -57,8 +57,8 @@ bool
 chunk_dss_prec_set(dss_prec_t dss_prec)
 {
 
-	if (config_dss == false)
-		return (true);
+	if (have_dss == false)
+		return (dss_prec != dss_prec_disabled);
 	malloc_mutex_lock(&dss_mtx);
 	dss_prec_default = dss_prec;
 	malloc_mutex_unlock(&dss_mtx);
@@ -70,7 +70,7 @@ chunk_alloc_dss(size_t size, size_t alignment, bool *zero)
 {
 	void *ret;
 
-	cassert(config_dss);
+	cassert(have_dss);
 	assert(size > 0 && (size & chunksize_mask) == 0);
 	assert(alignment > 0 && (alignment & chunksize_mask) == 0);
 
@@ -143,7 +143,7 @@ chunk_in_dss(void *chunk)
 {
 	bool ret;
 
-	cassert(config_dss);
+	cassert(have_dss);
 
 	malloc_mutex_lock(&dss_mtx);
 	if ((uintptr_t)chunk >= (uintptr_t)dss_base
@@ -160,7 +160,7 @@ bool
 chunk_dss_boot(void)
 {
 
-	cassert(config_dss);
+	cassert(have_dss);
 
 	if (malloc_mutex_init(&dss_mtx))
 		return (true);
@@ -175,7 +175,7 @@ void
 chunk_dss_prefork(void)
 {
 
-	if (config_dss)
+	if (have_dss)
 		malloc_mutex_prefork(&dss_mtx);
 }
 
@@ -183,7 +183,7 @@ void
 chunk_dss_postfork_parent(void)
 {
 
-	if (config_dss)
+	if (have_dss)
 		malloc_mutex_postfork_parent(&dss_mtx);
 }
 
@@ -191,7 +191,7 @@ void
 chunk_dss_postfork_child(void)
 {
 
-	if (config_dss)
+	if (have_dss)
 		malloc_mutex_postfork_child(&dss_mtx);
 }
 
diff --git a/src/ctl.c b/src/ctl.c
index cc2c5ae..0340a27 100644
--- a/src/ctl.c
+++ b/src/ctl.c
@@ -74,7 +74,6 @@ CTL_PROTO(thread_allocatedp)
 CTL_PROTO(thread_deallocated)
 CTL_PROTO(thread_deallocatedp)
 CTL_PROTO(config_debug)
-CTL_PROTO(config_dss)
 CTL_PROTO(config_fill)
 CTL_PROTO(config_lazy_lock)
 CTL_PROTO(config_mremap)
@@ -213,7 +212,6 @@ static const ctl_named_node_t	thread_node[] = {
 
 static const ctl_named_node_t	config_node[] = {
 	{NAME("debug"),			CTL(config_debug)},
-	{NAME("dss"),			CTL(config_dss)},
 	{NAME("fill"),			CTL(config_fill)},
 	{NAME("lazy_lock"),		CTL(config_lazy_lock)},
 	{NAME("mremap"),		CTL(config_mremap)},
@@ -1136,7 +1134,6 @@ label_return:
 /******************************************************************************/
 
 CTL_RO_BOOL_CONFIG_GEN(config_debug)
-CTL_RO_BOOL_CONFIG_GEN(config_dss)
 CTL_RO_BOOL_CONFIG_GEN(config_fill)
 CTL_RO_BOOL_CONFIG_GEN(config_lazy_lock)
 CTL_RO_BOOL_CONFIG_GEN(config_mremap)
@@ -1356,8 +1353,7 @@ arena_i_dss_ctl(const size_t *mib, size_t miblen, void *oldp, size_t *oldlenp,
 		arena_t *arena = arenas[arena_ind];
 		if (arena != NULL) {
 			dss_prec_old = arena_dss_prec_get(arena);
-			arena_dss_prec_set(arena, dss_prec);
-			err = false;
+			err = arena_dss_prec_set(arena, dss_prec);
 		} else
 			err = true;
 	} else {
diff --git a/src/huge.c b/src/huge.c
index d72f213..e725fd9 100644
--- a/src/huge.c
+++ b/src/huge.c
@@ -140,7 +140,7 @@ huge_ralloc(void *ptr, size_t oldsize, size_t size, size_t extra,
 	 * Use mremap(2) if this is a huge-->huge reallocation, and neither the
 	 * source nor the destination are in dss.
 	 */
-	if (oldsize >= chunksize && (config_dss == false || (chunk_in_dss(ptr)
+	if (oldsize >= chunksize && (have_dss == false || (chunk_in_dss(ptr)
 	    == false && chunk_in_dss(ret) == false))) {
 		size_t newsize = huge_salloc(ret);
 
@@ -198,12 +198,12 @@ static void
 huge_dalloc_junk(void *ptr, size_t usize)
 {
 
-	if (config_fill && config_dss && opt_junk) {
+	if (config_fill && have_dss && opt_junk) {
 		/*
 		 * Only bother junk filling if the chunk isn't about to be
 		 * unmapped.
 		 */
-		if (config_munmap == false || (config_dss && chunk_in_dss(ptr)))
+		if (config_munmap == false || (have_dss && chunk_in_dss(ptr)))
 			memset(ptr, 0x5a, usize);
 	}
 }
diff --git a/test/integration/MALLOCX_ARENA.c b/test/integration/MALLOCX_ARENA.c
index 695a5b6..30c203a 100644
--- a/test/integration/MALLOCX_ARENA.c
+++ b/test/integration/MALLOCX_ARENA.c
@@ -2,6 +2,14 @@
 
 #define	NTHREADS 10
 
+static bool have_dss =
+#ifdef JEMALLOC_DSS
+    true
+#else
+    false
+#endif
+    ;
+
 void *
 thd_start(void *arg)
 {
@@ -18,13 +26,16 @@ thd_start(void *arg)
 		size_t mib[3];
 		size_t miblen = sizeof(mib) / sizeof(size_t);
 		const char *dss_precs[] = {"disabled", "primary", "secondary"};
-		const char *dss = dss_precs[thread_ind %
-		    (sizeof(dss_precs)/sizeof(char*))];
+		unsigned prec_ind = thread_ind %
+		    (sizeof(dss_precs)/sizeof(char*));
+		const char *dss = dss_precs[prec_ind];
+		int expected_err = (have_dss || prec_ind == 0) ? 0 : EFAULT;
 		assert_d_eq(mallctlnametomib("arena.0.dss", mib, &miblen), 0,
 		    "Error in mallctlnametomib()");
 		mib[1] = arena_ind;
 		assert_d_eq(mallctlbymib(mib, miblen, NULL, NULL, (void *)&dss,
-		    sizeof(const char *)), 0, "Error in mallctlbymib()");
+		    sizeof(const char *)), expected_err,
+		    "Error in mallctlbymib()");
 	}
 
 	p = mallocx(1, MALLOCX_ARENA(arena_ind));
diff --git a/test/unit/mallctl.c b/test/unit/mallctl.c
index 31fb810..caf20f8 100644
--- a/test/unit/mallctl.c
+++ b/test/unit/mallctl.c
@@ -127,7 +127,6 @@ TEST_BEGIN(test_mallctl_config)
 } while (0)
 
 	TEST_MALLCTL_CONFIG(debug);
-	TEST_MALLCTL_CONFIG(dss);
 	TEST_MALLCTL_CONFIG(fill);
 	TEST_MALLCTL_CONFIG(lazy_lock);
 	TEST_MALLCTL_CONFIG(mremap);
@@ -255,15 +254,28 @@ TEST_BEGIN(test_arena_i_dss)
 {
 	const char *dss_prec_old, *dss_prec_new;
 	size_t sz = sizeof(dss_prec_old);
+	size_t mib[3];
+	size_t miblen;
+
+	miblen = sizeof(mib)/sizeof(size_t);
+	assert_d_eq(mallctlnametomib("arena.0.dss", mib, &miblen), 0,
+	    "Unexpected mallctlnametomib() error");
 
-	dss_prec_new = "primary";
-	assert_d_eq(mallctl("arena.0.dss", &dss_prec_old, &sz, &dss_prec_new,
+	dss_prec_new = "disabled";
+	assert_d_eq(mallctlbymib(mib, miblen, &dss_prec_old, &sz, &dss_prec_new,
 	    sizeof(dss_prec_new)), 0, "Unexpected mallctl() failure");
 	assert_str_ne(dss_prec_old, "primary",
 	    "Unexpected default for dss precedence");
 
-	assert_d_eq(mallctl("arena.0.dss", &dss_prec_new, &sz, &dss_prec_old,
+	assert_d_eq(mallctlbymib(mib, miblen, &dss_prec_new, &sz, &dss_prec_old,
 	    sizeof(dss_prec_old)), 0, "Unexpected mallctl() failure");
+
+	mib[1] = narenas_total_get();
+	dss_prec_new = "disabled";
+	assert_d_eq(mallctlbymib(mib, miblen, &dss_prec_old, &sz, &dss_prec_new,
+	    sizeof(dss_prec_new)), 0, "Unexpected mallctl() failure");
+	assert_str_ne(dss_prec_old, "primary",
+	    "Unexpected default for dss precedence");
 }
 TEST_END