Remove the opt.lg_prof_bt_max option.

Remove opt.lg_prof_bt_max, and hard code it to 7.  The original
intention of this option was to enable faster backtracing by limiting
backtrace depth.  However, this makes graphical pprof output very
difficult to interpret.  In practice, decreasing sampling frequency is a
better mechanism for limiting profiling overhead.

4 files changed, 8 insertions, 25 deletions

diff --git a/src/ctl.c b/src/ctl.c
index 12b4185..4938e10 100644
--- a/src/ctl.c
+++ b/src/ctl.c
@@ -74,7 +74,6 @@ CTL_PROTO(opt_lg_tcache_gc_sweep)
 CTL_PROTO(opt_prof)
 CTL_PROTO(opt_prof_prefix)
 CTL_PROTO(opt_prof_active)
-CTL_PROTO(opt_lg_prof_bt_max)
 CTL_PROTO(opt_lg_prof_sample)
 CTL_PROTO(opt_lg_prof_interval)
 CTL_PROTO(opt_prof_gdump)
@@ -216,7 +215,6 @@ static const ctl_node_t opt_node[] = {
 	{NAME("prof"),			CTL(opt_prof)},
 	{NAME("prof_prefix"),		CTL(opt_prof_prefix)},
 	{NAME("prof_active"),		CTL(opt_prof_active)},
-	{NAME("lg_prof_bt_max"),	CTL(opt_lg_prof_bt_max)},
 	{NAME("lg_prof_sample"),	CTL(opt_lg_prof_sample)},
 	{NAME("lg_prof_interval"),	CTL(opt_lg_prof_interval)},
 	{NAME("prof_gdump"),		CTL(opt_prof_gdump)},
@@ -1125,7 +1123,6 @@ CTL_RO_NL_CGEN(config_tcache, opt_lg_tcache_gc_sweep, opt_lg_tcache_gc_sweep,
 CTL_RO_NL_CGEN(config_prof, opt_prof, opt_prof, bool)
 CTL_RO_NL_CGEN(config_prof, opt_prof_prefix, opt_prof_prefix, const char *)
 CTL_RO_CGEN(config_prof, opt_prof_active, opt_prof_active, bool) /* Mutable. */
-CTL_RO_NL_CGEN(config_prof, opt_lg_prof_bt_max, opt_lg_prof_bt_max, size_t)
 CTL_RO_NL_CGEN(config_prof, opt_lg_prof_sample, opt_lg_prof_sample, size_t)
 CTL_RO_NL_CGEN(config_prof, opt_lg_prof_interval, opt_lg_prof_interval, ssize_t)
 CTL_RO_NL_CGEN(config_prof, opt_prof_gdump, opt_prof_gdump, bool)
diff --git a/src/jemalloc.c b/src/jemalloc.c
index d2a6009..81829fe 100644
--- a/src/jemalloc.c
+++ b/src/jemalloc.c
@@ -597,8 +597,6 @@ malloc_conf_init(void)
 			if (config_prof) {
 				CONF_HANDLE_BOOL(prof)
 				CONF_HANDLE_CHAR_P(prof_prefix, "jeprof")
-				CONF_HANDLE_SIZE_T(lg_prof_bt_max, 0,
-				    LG_PROF_BT_MAX)
 				CONF_HANDLE_BOOL(prof_active)
 				CONF_HANDLE_SSIZE_T(lg_prof_sample, 0,
 				    (sizeof(uint64_t) << 3) - 1)
diff --git a/src/prof.c b/src/prof.c
index a4012f0..21b60e3 100644
--- a/src/prof.c
+++ b/src/prof.c
@@ -16,7 +16,6 @@
 
 bool		opt_prof = false;
 bool		opt_prof_active = true;
-size_t		opt_lg_prof_bt_max = LG_PROF_BT_MAX_DEFAULT;
 size_t		opt_lg_prof_sample = LG_PROF_SAMPLE_DEFAULT;
 ssize_t		opt_lg_prof_interval = LG_PROF_INTERVAL_DEFAULT;
 bool		opt_prof_gdump = false;
@@ -27,8 +26,6 @@ char		opt_prof_prefix[PATH_MAX + 1];
 uint64_t	prof_interval;
 bool		prof_promote;
 
-unsigned	prof_bt_max;
-
 #ifndef NO_TLS
 __thread prof_tdata_t	*prof_tdata_tls
     JEMALLOC_ATTR(tls_model("initial-exec"));
@@ -179,7 +176,7 @@ prof_leave(void)
 
 #ifdef JEMALLOC_PROF_LIBUNWIND
 void
-prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
+prof_backtrace(prof_bt_t *bt, unsigned nignore)
 {
 	unw_context_t uc;
 	unw_cursor_t cursor;
@@ -189,7 +186,6 @@ prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
 	cassert(config_prof);
 	assert(bt->len == 0);
 	assert(bt->vec != NULL);
-	assert(max <= (1U << opt_lg_prof_bt_max));
 
 	unw_getcontext(&uc);
 	unw_init_local(&cursor, &uc);
@@ -205,7 +201,7 @@ prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
 	 * Iterate over stack frames until there are no more, or until no space
 	 * remains in bt.
 	 */
-	for (i = 0; i < max; i++) {
+	for (i = 0; i < PROF_BT_MAX; i++) {
 		unw_get_reg(&cursor, UNW_REG_IP, (unw_word_t *)&bt->vec[i]);
 		bt->len++;
 		err = unw_step(&cursor);
@@ -243,9 +239,9 @@ prof_unwind_callback(struct _Unwind_Context *context, void *arg)
 }
 
 void
-prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
+prof_backtrace(prof_bt_t *bt, unsigned nignore)
 {
-	prof_unwind_data_t data = {bt, nignore, max};
+	prof_unwind_data_t data = {bt, nignore, PROF_BT_MAX};
 
 	cassert(config_prof);
 
@@ -253,10 +249,10 @@ prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
 }
 #elif (defined(JEMALLOC_PROF_GCC))
 void
-prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
+prof_backtrace(prof_bt_t *bt, unsigned nignore)
 {
 #define	BT_FRAME(i)							\
-	if ((i) < nignore + max) {					\
+	if ((i) < nignore + PROF_BT_MAX) {				\
 		void *p;						\
 		if (__builtin_frame_address(i) == 0)			\
 			return;						\
@@ -272,7 +268,6 @@ prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
 
 	cassert(config_prof);
 	assert(nignore <= 3);
-	assert(max <= (1U << opt_lg_prof_bt_max));
 
 	BT_FRAME(0)
 	BT_FRAME(1)
@@ -423,7 +418,7 @@ prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
 }
 #else
 void
-prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
+prof_backtrace(prof_bt_t *bt, unsigned nignore)
 {
 
 	cassert(config_prof);
@@ -1168,7 +1163,7 @@ prof_tdata_init(void)
 	}
 	ql_new(&prof_tdata->lru_ql);
 
-	prof_tdata->vec = imalloc(sizeof(void *) * prof_bt_max);
+	prof_tdata->vec = imalloc(sizeof(void *) * PROF_BT_MAX);
 	if (prof_tdata->vec == NULL) {
 		ckh_delete(&prof_tdata->bt2cnt);
 		idalloc(prof_tdata);
@@ -1270,7 +1265,6 @@ prof_boot2(void)
 			abort();
 		}
 
-		prof_bt_max = (1U << opt_lg_prof_bt_max);
 		if (malloc_mutex_init(&prof_dump_seq_mtx))
 			return (true);
 
diff --git a/src/stats.c b/src/stats.c
index 86a48c6..6d9ba9d 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -511,7 +511,6 @@ stats_print(void (*write_cb)(void *, const char *), void *cbopaque,
 		OPT_WRITE_SSIZE_T(lg_tcache_max)
 		OPT_WRITE_BOOL(prof)
 		OPT_WRITE_CHAR_P(prof_prefix)
-		OPT_WRITE_SIZE_T(lg_prof_bt_max)
 		OPT_WRITE_BOOL(prof_active)
 		OPT_WRITE_SSIZE_T(lg_prof_sample)
 		OPT_WRITE_BOOL(prof_accum)
@@ -616,11 +615,6 @@ stats_print(void (*write_cb)(void *, const char *), void *cbopaque,
 		}
 		if ((err = JEMALLOC_P(mallctl)("opt.prof", &bv, &bsz, NULL, 0))
 		   == 0 && bv) {
-			CTL_GET("opt.lg_prof_bt_max", &sv, size_t);
-			write_cb(cbopaque, "Maximum profile backtrace depth: ");
-			write_cb(cbopaque, u2s((1U << sv), 10, s));
-			write_cb(cbopaque, "\n");
-
 			CTL_GET("opt.lg_prof_sample", &sv, size_t);
 			write_cb(cbopaque, "Average profile sample interval: ");
 			write_cb(cbopaque, u2s((((uint64_t)1U) << sv), 10, s));