Add switch for disabling sys_alloc carriers

The switch "+Musac <boolean>" controls if sys_alloc carriers
are allowed.

5 files changed, 33 insertions, 9 deletions

diff --git a/erts/doc/src/erts_alloc.xml b/erts/doc/src/erts_alloc.xml
index 90bc35cdc9..70029dbeab 100644
--- a/erts/doc/src/erts_alloc.xml
+++ b/erts/doc/src/erts_alloc.xml
@@ -549,6 +549,11 @@
        placed in separate memory segments. When this limit has been
        reached, new carriers will be placed in memory retrieved from
       <c>sys_alloc</c>.</item>
+      <tag><marker id="Musac"><c><![CDATA[+Musac <bool>]]></c></marker></tag>
+      <item>
+	Allow <c>sys_alloc</c> carriers. By default <c>true</c>. If
+	set to <c>false</c>, <c>sys_alloc</c> carriers will never be
+	created by allocators using the <c>alloc_util</c> framework.</item>
     </taglist>
     <p>Instrumentation flags:</p>
     <taglist>
diff --git a/erts/emulator/beam/erl_alloc.c b/erts/emulator/beam/erl_alloc.c
index 8e20d58161..fb0f47d1b7 100644
--- a/erts/emulator/beam/erl_alloc.c
+++ b/erts/emulator/beam/erl_alloc.c
@@ -1670,6 +1670,10 @@ handle_args(int *argc, char **argv, erts_alc_hndl_args_init_t *init)
 			init->alloc_util.mmc
 			    = get_amount_value(argv[i]+6, argv, &i);
 		    }
+		    else if (has_prefix("sac", argv[i]+3)) {
+			init->alloc_util.sac
+			    = get_bool_value(argv[i]+6, argv, &i);
+		    }
 		    else {
 			int a;
 			int start = i;
diff --git a/erts/emulator/beam/erl_alloc_util.c b/erts/emulator/beam/erl_alloc_util.c
index 1fdee4db2c..b0fc653f32 100644
--- a/erts/emulator/beam/erl_alloc_util.c
+++ b/erts/emulator/beam/erl_alloc_util.c
@@ -98,6 +98,7 @@ static Uint sys_alloc_carrier_size;
 #if HAVE_ERTS_MSEG
 static Uint max_mseg_carriers;
 #endif
+static int allow_sys_alloc_carriers;
 
 #define ONE_GIGA (1000000000)
 
@@ -3256,13 +3257,15 @@ create_carrier(Allctr_t *allctr, Uint umem_sz, UWord flags)
     int is_mseg = 0;
 #endif
 
-#if HALFWORD_HEAP
-    flags |= CFLG_FORCE_MSEG;
-#elif ERTS_SUPER_ALIGNED_MSEG_ONLY
-    if (flags & CFLG_MBC) {
+    if (HALFWORD_HEAP
+	|| (ERTS_SUPER_ALIGNED_MSEG_ONLY && (flags & CFLG_MBC))
+	|| !allow_sys_alloc_carriers) {
 	flags |= CFLG_FORCE_MSEG;
-    }
+	flags &= ~CFLG_FORCE_SYS_ALLOC;
+#if !HAVE_ERTS_MSEG
+	return NULL;
 #endif
+    }
 
     ASSERT((flags & CFLG_SBC && !(flags & CFLG_MBC))
 	   || (flags & CFLG_MBC && !(flags & CFLG_SBC)));
@@ -3697,6 +3700,7 @@ static struct {
     Eterm mmc;
 #endif
     Eterm ycs;
+    Eterm sac;
 
     Eterm fix_types;
 
@@ -3789,6 +3793,7 @@ init_atoms(Allctr_t *allctr)
 	AM_INIT(mmc);
 #endif
 	AM_INIT(ycs);
+	AM_INIT(sac);
 
 	AM_INIT(fix_types);
 
@@ -4509,17 +4514,22 @@ erts_alcu_au_info_options(int *print_to_p, void *print_to_arg,
 #if HAVE_ERTS_MSEG
 		   "option mmc: %beu\n"
 #endif
-		   "option ycs: %beu\n",
+		   "option ycs: %beu\n"
+		   "option sac: %s\n",
 #if HAVE_ERTS_MSEG
 		   max_mseg_carriers,
 #endif
-		   sys_alloc_carrier_size);
+		   sys_alloc_carrier_size,
+		   allow_sys_alloc_carriers ? "true" : "false");
     }
 
     if (hpp || szp) {
 	res = NIL;
 	ensure_atoms_initialized(NULL);
 	add_2tup(hpp, szp, &res,
+		 am.sac,
+		 allow_sys_alloc_carriers ? am_true : am_false);
+	add_2tup(hpp, szp, &res,
 		 am.ycs,
 		 bld_uint(hpp, szp, sys_alloc_carrier_size));
 #if HAVE_ERTS_MSEG
@@ -5681,6 +5691,7 @@ erts_alcu_init(AlcUInit_t *init)
 #else /* #if HAVE_ERTS_MSEG */
     sys_alloc_carrier_size = ((init->ycs + 4095) / 4096) * 4096;
 #endif
+    allow_sys_alloc_carriers = init->sac;
 
 #ifdef DEBUG
     carrier_alignment = sizeof(Unit_t);
diff --git a/erts/emulator/beam/erl_alloc_util.h b/erts/emulator/beam/erl_alloc_util.h
index 222f137024..7be6b1ed9d 100644
--- a/erts/emulator/beam/erl_alloc_util.h
+++ b/erts/emulator/beam/erl_alloc_util.h
@@ -32,6 +32,7 @@ typedef struct Allctr_t_ Allctr_t;
 typedef struct {
     UWord ycs;
     UWord mmc;
+    int   sac;
 } AlcUInit_t;
 
 typedef struct {
@@ -75,7 +76,8 @@ typedef struct {
 
 #define ERTS_DEFAULT_ALCU_INIT {                                           \
     1024*1024,		/* (bytes)  ycs:    sys_alloc carrier size       */\
-    ~((UWord) 0)	/* (amount) mmc:    max mseg carriers            */ \
+    ~((UWord) 0),	/* (amount) mmc:    max mseg carriers            */\
+    1			/* (bool)   sac:    sys_alloc carriers           */\
 }
 
 #define ERTS_DEFAULT_ALLCTR_INIT {                                         \
@@ -109,7 +111,8 @@ typedef struct {
 
 #define ERTS_DEFAULT_ALCU_INIT {                                           \
     128*1024,		/* (bytes)  ycs:    sys_alloc carrier size       */\
-    1024      		/* (amount) mmc:    max mseg carriers            */\
+    1024,      		/* (amount) mmc:    max mseg carriers            */\
+    1			/* (bool)   sac:    sys_alloc carriers           */\
 }
 
 #define ERTS_DEFAULT_ALLCTR_INIT {                                         \
diff --git a/erts/etc/common/erlexec.c b/erts/etc/common/erlexec.c
index ffbefce545..6fd3dd83e2 100644
--- a/erts/etc/common/erlexec.c
+++ b/erts/etc/common/erlexec.c
@@ -103,6 +103,7 @@ static char *plusM_other_switches[] = {
     "ea",
     "ummc",
     "uycs",
+    "usac",
     "im",
     "is",
     "it",