Add arena-specific and selective dss allocation.

Add the "arenas.extend" mallctl, so that it is possible to create new
arenas that are outside the set that jemalloc automatically multiplexes
threads onto.

Add the ALLOCM_ARENA() flag for {,r,d}allocm(), so that it is possible
to explicitly allocate from a particular arena.

Add the "opt.dss" mallctl, which controls the default precedence of dss
allocation relative to mmap allocation.

Add the "arena.<i>.dss" mallctl, which makes it possible to set the
default dss precedence on a per arena or global basis.

Add the "arena.<i>.purge" mallctl, which obsoletes "arenas.purge".

Add the "stats.arenas.<i>.dss" mallctl.

test/ALLOCM_ARENA.c

@@ -0,0 +1,66 @@
+#define	JEMALLOC_MANGLE
+#include "jemalloc_test.h"
+
+#define	NTHREADS 10
+
+void *
+je_thread_start(void *arg)
+{
+	unsigned thread_ind = (unsigned)(uintptr_t)arg;
+	unsigned arena_ind;
+	int r;
+	void *p;
+	size_t rsz, sz;
+
+	sz = sizeof(arena_ind);
+	if (mallctl("arenas.extend", &arena_ind, &sz, NULL, 0)
+	    != 0) {
+		malloc_printf("Error in arenas.extend\n");
+		abort();
+	}
+
+	if (thread_ind % 4 != 3) {
+		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 % 4];
+		if (mallctlnametomib("arena.0.dss", mib, &miblen) != 0) {
+			malloc_printf("Error in mallctlnametomib()\n");
+			abort();
+		}
+		mib[1] = arena_ind;
+		if (mallctlbymib(mib, miblen, NULL, NULL, (void *)&dss,
+		    sizeof(const char *))) {
+			malloc_printf("Error in mallctlbymib()\n");
+			abort();
+		}
+	}
+
+	r = allocm(&p, &rsz, 1, ALLOCM_ARENA(arena_ind));
+	if (r != ALLOCM_SUCCESS) {
+		malloc_printf("Unexpected allocm() error\n");
+		abort();
+	}
+
+	return (NULL);
+}
+
+int
+main(void)
+{
+	je_thread_t threads[NTHREADS];
+	unsigned i;
+
+	malloc_printf("Test begin\n");
+
+	for (i = 0; i < NTHREADS; i++) {
+		je_thread_create(&threads[i], je_thread_start,
+		    (void *)(uintptr_t)i);
+	}
+
+	for (i = 0; i < NTHREADS; i++)
+		je_thread_join(threads[i], NULL);
+
+	malloc_printf("Test end\n");
+	return (0);
+}

test/ALLOCM_ARENA.exp

@@ -0,0 +1,2 @@
+Test begin
+Test end

test/thread_arena.c

@@ -1,7 +1,7 @@
 #define	JEMALLOC_MANGLE
 #include "jemalloc_test.h"
 
-#define NTHREADS 10
+#define	NTHREADS 10
 
 void *
 je_thread_start(void *arg)
@@ -66,8 +66,10 @@ main(void)
 		goto label_return;
 	}
 
-	for (i = 0; i < NTHREADS; i++)
-		je_thread_create(&threads[i], je_thread_start, (void *)&arena_ind);
+	for (i = 0; i < NTHREADS; i++) {
+		je_thread_create(&threads[i], je_thread_start,
+		    (void *)&arena_ind);
+	}
 
 	for (i = 0; i < NTHREADS; i++)
 		je_thread_join(threads[i], (void *)&ret);