Add stats: arena uptime.

doc/jemalloc.xml.in

@@ -2280,6 +2280,18 @@ struct extent_hooks_s {
         arena.</para></listitem>
       </varlistentry>
 
+      <varlistentry id="stats.arenas.i.uptime">
+        <term>
+          <mallctl>stats.arenas.&lt;i&gt;.uptime</mallctl>
+          (<type>uint64_t</type>)
+          <literal>r-</literal>
+        </term>
+        <listitem><para>Time elapsed (in nanoseconds) since the arena was
+        created.  If &lt;i&gt; equals <constant>0</constant> or
+        <constant>MALLCTL_ARENAS_ALL</constant>, this is the uptime since malloc
+        initialization.</para></listitem>
+      </varlistentry>
+
       <varlistentry id="stats.arenas.i.pactive">
         <term>
           <mallctl>stats.arenas.&lt;i&gt;.pactive</mallctl>

include/jemalloc/internal/arena_structs_b.h

@@ -261,6 +261,8 @@ struct arena_s {
 	 * Synchronization: internal.
 	 */
 	base_t			*base;
+	/* Used to determine uptime.  Read-only after initialization. */
+	nstime_t		create_time;
 };
 
 /* Used in conjunction with tsd for fast arena-related context lookup. */

include/jemalloc/internal/stats.h

@@ -145,6 +145,9 @@ typedef struct arena_stats_s {
 
 	/* One element for each large size class. */
 	malloc_large_stats_t	lstats[NSIZES - NBINS];
+
+	/* Arena uptime. */
+	nstime_t		uptime;
 } arena_stats_t;
 
 #endif /* JEMALLOC_INTERNAL_STATS_H */

src/arena.c

@@ -330,6 +330,10 @@ arena_stats_merge(tsdn_t *tsdn, arena_t *arena, unsigned *nthreads,
 	    arena_prof_mutex_base)
 #undef READ_ARENA_MUTEX_PROF_DATA
 
+	nstime_copy(&astats->uptime, &arena->create_time);
+	nstime_update(&astats->uptime);
+	nstime_subtract(&astats->uptime, &arena->create_time);
+
 	for (szind_t i = 0; i < NBINS; i++) {
 		arena_bin_t *bin = &arena->bins[i];
 
@@ -1965,6 +1969,9 @@ arena_new(tsdn_t *tsdn, unsigned ind, extent_hooks_t *extent_hooks) {
 
 	arena->base = base;
 
+	nstime_init(&arena->create_time, 0);
+	nstime_update(&arena->create_time);
+
 	/* We don't support reetrancy for arena 0 bootstrapping. */
 	if (ind != 0 && hooks_arena_new_hook) {
 		/*

src/ctl.c

@@ -157,6 +157,7 @@ CTL_PROTO(stats_arenas_i_lextents_j_nrequests)
 CTL_PROTO(stats_arenas_i_lextents_j_curlextents)
 INDEX_PROTO(stats_arenas_i_lextents_j)
 CTL_PROTO(stats_arenas_i_nthreads)
+CTL_PROTO(stats_arenas_i_uptime)
 CTL_PROTO(stats_arenas_i_dss)
 CTL_PROTO(stats_arenas_i_dirty_decay_time)
 CTL_PROTO(stats_arenas_i_muzzy_decay_time)
@@ -441,6 +442,7 @@ MUTEX_PROF_ARENA_MUTEXES
 
 static const ctl_named_node_t stats_arenas_i_node[] = {
 	{NAME("nthreads"),	CTL(stats_arenas_i_nthreads)},
+	{NAME("uptime"),	CTL(stats_arenas_i_uptime)},
 	{NAME("dss"),		CTL(stats_arenas_i_dss)},
 	{NAME("dirty_decay_time"), CTL(stats_arenas_i_dirty_decay_time)},
 	{NAME("muzzy_decay_time"), CTL(stats_arenas_i_muzzy_decay_time)},
@@ -778,6 +780,10 @@ MUTEX_PROF_ARENA_MUTEXES
 		accum_atomic_zu(&sdstats->astats.tcache_bytes,
 		    &astats->astats.tcache_bytes);
 
+		if (ctl_arena->arena_ind == 0) {
+			sdstats->astats.uptime = astats->astats.uptime;
+		}
+
 		for (i = 0; i < NBINS; i++) {
 			sdstats->bstats[i].nmalloc += astats->bstats[i].nmalloc;
 			sdstats->bstats[i].ndalloc += astats->bstats[i].ndalloc;
@@ -2317,6 +2323,8 @@ CTL_RO_GEN(stats_arenas_i_dirty_decay_time, arenas_i(mib[2])->dirty_decay_time,
 CTL_RO_GEN(stats_arenas_i_muzzy_decay_time, arenas_i(mib[2])->muzzy_decay_time,
     ssize_t)
 CTL_RO_GEN(stats_arenas_i_nthreads, arenas_i(mib[2])->nthreads, unsigned)
+CTL_RO_GEN(stats_arenas_i_uptime,
+    nstime_ns(&arenas_i(mib[2])->astats->astats.uptime), uint64_t)
 CTL_RO_GEN(stats_arenas_i_pactive, arenas_i(mib[2])->pactive, size_t)
 CTL_RO_GEN(stats_arenas_i_pdirty, arenas_i(mib[2])->pdirty, size_t)
 CTL_RO_GEN(stats_arenas_i_pmuzzy, arenas_i(mib[2])->pmuzzy, size_t)

src/stats.c

@@ -421,6 +421,7 @@ stats_arena_print(void (*write_cb)(void *, const char *), void *cbopaque,
 	size_t large_allocated;
 	uint64_t large_nmalloc, large_ndalloc, large_nrequests;
 	size_t tcache_bytes;
+	uint64_t uptime;
 
 	CTL_GET("arenas.page", &page, size_t);
 
@@ -433,6 +434,15 @@ stats_arena_print(void (*write_cb)(void *, const char *), void *cbopaque,
 		    "assigned threads: %u\n", nthreads);
 	}
 
+	CTL_M2_GET("stats.arenas.0.uptime", i, &uptime, uint64_t);
+	if (json) {
+		malloc_cprintf(write_cb, cbopaque,
+		    "\t\t\t\t\"uptime_ns\": %"FMTu64",\n", uptime);
+	} else {
+		malloc_cprintf(write_cb, cbopaque,
+		    "uptime: %"FMTu64"\n", uptime);
+	}
+
 	CTL_M2_GET("stats.arenas.0.dss", i, &dss, const char *);
 	if (json) {
 		malloc_cprintf(write_cb, cbopaque,