Implement sampling for heap profiling.

jemalloc/configure.ac

@@ -647,6 +647,7 @@ if test "x$enable_tls" = "x0" ; then
   enable_prof="0"
 fi
 if test "x$enable_prof" = "x1" ; then
+  LIBS="$LIBS -lm"
   AC_DEFINE([JEMALLOC_PROF], [ ])
   if test "x$enable_prof_libunwind" = "x1" ; then
     AC_CHECK_HEADERS([libunwind.h], , [enable_prof_libunwind="0"])

jemalloc/doc/jemalloc.3.in

@@ -38,7 +38,7 @@
 .\"     @(#)malloc.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD: head/lib/libc/stdlib/malloc.3 182225 2008-08-27 02:00:53Z jasone $
 .\"
-.Dd February 11, 2010
+.Dd March 1, 2010
 .Dt JEMALLOC 3
 .Os
 .Sh NAME
@@ -355,6 +355,9 @@ will disable dirty page purging.
 @roff_prof@.Dq B
 @roff_prof@option for backtrace depth control.
 @roff_prof@See the
+@roff_prof@.Dq S
+@roff_prof@option for probabilistic sampling control.
+@roff_prof@See the
 @roff_prof@.Dq I
 @roff_prof@option for information on interval-triggered profile dumping, and the
 @roff_prof@.Dq U
@@ -464,6 +467,15 @@ Double/halve the size of the maximum size class that is a multiple of the
 quantum (8 or 16 bytes, depending on architecture).
 Above this size, cacheline spacing is used for size classes.
 The default value is 128 bytes.
+@roff_prof@.It S
+@roff_prof@Double/halve the average interval between allocation samples, as
+@roff_prof@measured in bytes of allocation activity.
+@roff_prof@Increasing the sampling interval decreases profile fidelity, but
+@roff_prof@also decreases the computational overhead.
+@roff_prof@The default sample interval is one (i.e. all allocations are
+@roff_prof@sampled).
+@roff_prof@A sample interval greater than one implicitly disables leak
+@roff_prof@reporting.
 @roff_prof@.It U
 @roff_prof@Trigger a memory profile dump every time the total virtual memory
 @roff_prof@exceeds the previous maximum.

jemalloc/include/jemalloc/internal/prn.h

@@ -25,7 +25,7 @@
  *   uint32_t state      : Seed value.
  *   const uint32_t a, c : See above discussion.
  */
-#define prn(r, lg_range, state, a, c) do {				\
+#define prn32(r, lg_range, state, a, c) do {				\
 	assert(lg_range > 0);						\
 	assert(lg_range <= 32);						\
 									\
@@ -34,6 +34,16 @@
 	r >>= (32 - lg_range);						\
 } while (false)
 
+/* Same as prn32(), but 64 bits of pseudo-randomness, using uint64_t. */
+#define prn64(r, lg_range, state, a, c) do {				\
+	assert(lg_range > 0);						\
+	assert(lg_range <= 64);						\
+									\
+	r = (state * (a)) + (c);					\
+	state = r;							\
+	r >>= (64 - lg_range);						\
+} while (false)
+
 #endif /* JEMALLOC_H_TYPES */
 /******************************************************************************/
 #ifdef JEMALLOC_H_STRUCTS

jemalloc/include/jemalloc/internal/prof.h

@@ -8,6 +8,9 @@ typedef struct prof_thr_cnt_s prof_thr_cnt_t;
 typedef struct prof_ctx_s prof_ctx_t;
 typedef struct prof_s prof_t;
 
+/* Option defaults. */
+#define	LG_PROF_BT_MAX_DEFAULT		2
+#define	LG_PROF_SAMPLE_DEFAULT		0
 #define	LG_PROF_INTERVAL_DEFAULT	30
 
 /*
@@ -16,7 +19,7 @@ typedef struct prof_s prof_t;
  * a hard-coded number of backtrace frame handlers, so increasing
  * LG_PROF_BT_MAX requires changing prof_backtrace().
  */
-#define	LG_PROF_BT_MAX		7
+#define	LG_PROF_BT_MAX		7 /* >= LG_PROF_BT_MAX_DEFAULT */
 #define	PROF_BT_MAX		(1U << LG_PROF_BT_MAX)
 
 /* Initial hash table size. */
@@ -117,7 +120,8 @@ struct prof_ctx_s {
 
 extern bool	opt_prof;
 extern size_t	opt_lg_prof_bt_max; /* Maximum backtrace depth. */
-extern size_t	opt_lg_prof_interval;
+extern size_t	opt_lg_prof_sample; /* Mean bytes between samples. */
+extern size_t	opt_lg_prof_interval; /* lg(prof_interval). */
 extern bool	opt_prof_udump; /* High-water memory dumping. */
 extern bool	opt_prof_leak; /* Dump leak summary at exit. */
 
@@ -133,7 +137,7 @@ extern uint64_t	prof_interval;
 bool	prof_init(prof_t *prof, bool master);
 void	prof_destroy(prof_t *prof);
 
-prof_thr_cnt_t	*prof_alloc_prep(void);
+prof_thr_cnt_t	*prof_alloc_prep(size_t size);
 prof_thr_cnt_t	*prof_cnt_get(const void *ptr);
 void	prof_malloc(const void *ptr, prof_thr_cnt_t *cnt);
 void	prof_realloc(const void *ptr, prof_thr_cnt_t *cnt, const void *old_ptr,

jemalloc/src/ckh.c

@@ -100,7 +100,7 @@ ckh_try_bucket_insert(ckh_t *ckh, size_t bucket, const void *key,
 	 * Cycle through the cells in the bucket, starting at a random position.
 	 * The randomness avoids worst-case search overhead as buckets fill up.
 	 */
-	prn(offset, LG_CKH_BUCKET_CELLS, ckh->prn_state, CKH_A, CKH_C);
+	prn32(offset, LG_CKH_BUCKET_CELLS, ckh->prn_state, CKH_A, CKH_C);
 	for (i = 0; i < (ZU(1) << LG_CKH_BUCKET_CELLS); i++) {
 		cell = &ckh->tab[(bucket << LG_CKH_BUCKET_CELLS) +
 		    ((i + offset) & ((ZU(1) << LG_CKH_BUCKET_CELLS) - 1))];
@@ -142,7 +142,7 @@ ckh_evict_reloc_insert(ckh_t *ckh, size_t argbucket, void const **argkey,
 		 * were an item for which both hashes indicated the same
 		 * bucket.
 		 */
-		prn(i, LG_CKH_BUCKET_CELLS, ckh->prn_state, CKH_A, CKH_C);
+		prn32(i, LG_CKH_BUCKET_CELLS, ckh->prn_state, CKH_A, CKH_C);
 		cell = &ckh->tab[(bucket << LG_CKH_BUCKET_CELLS) + i];
 		assert(cell->key != NULL);
 

jemalloc/src/ctl.c

@@ -69,6 +69,7 @@ CTL_PROTO(opt_lg_tcache_gc_sweep)
 #ifdef JEMALLOC_PROF
 CTL_PROTO(opt_prof)
 CTL_PROTO(opt_lg_prof_bt_max)
+CTL_PROTO(opt_lg_prof_sample)
 CTL_PROTO(opt_lg_prof_interval)
 CTL_PROTO(opt_prof_udump)
 CTL_PROTO(opt_prof_leak)
@@ -234,6 +235,7 @@ static const ctl_node_t opt_node[] = {
 #ifdef JEMALLOC_PROF
 	{NAME("prof"),			CTL(opt_prof)},
 	{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_udump"),		CTL(opt_prof_udump)},
 	{NAME("prof_leak"),		CTL(opt_prof_leak)},
@@ -1066,6 +1068,7 @@ CTL_RO_GEN(opt_lg_tcache_gc_sweep, opt_lg_tcache_gc_sweep, ssize_t)
 #ifdef JEMALLOC_PROF
 CTL_RO_GEN(opt_prof, opt_prof, bool)
 CTL_RO_GEN(opt_lg_prof_bt_max, opt_lg_prof_bt_max, size_t)
+CTL_RO_GEN(opt_lg_prof_sample, opt_lg_prof_sample, size_t)
 CTL_RO_GEN(opt_lg_prof_interval, opt_lg_prof_interval, size_t)
 CTL_RO_GEN(opt_prof_udump, opt_prof_udump, bool)
 CTL_RO_GEN(opt_prof_leak, opt_prof_leak, bool)

jemalloc/src/jemalloc.c

@@ -582,6 +582,15 @@ MALLOC_OUT:
 						opt_lg_qspace_max++;
 					break;
 #ifdef JEMALLOC_PROF
+				case 's':
+					if (opt_lg_prof_sample > 0)
+						opt_lg_prof_sample--;
+					break;
+				case 'S':
+					if (opt_lg_prof_sample + 1 <
+					    (sizeof(uint64_t) << 3))
+						opt_lg_prof_sample++;
+					break;
 				case 'u':
 					opt_prof_udump = false;
 					break;
@@ -870,7 +879,7 @@ JEMALLOC_P(malloc)(size_t size)
 	}
 
 #ifdef JEMALLOC_PROF
-	if (opt_prof && (cnt = prof_alloc_prep()) == NULL) {
+	if (opt_prof && (cnt = prof_alloc_prep(size)) == NULL) {
 		ret = NULL;
 		goto OOM;
 	}
@@ -955,7 +964,7 @@ JEMALLOC_P(posix_memalign)(void **memptr, size_t alignment, size_t size)
 		}
 
 #ifdef JEMALLOC_PROF
-		if (opt_prof && (cnt = prof_alloc_prep()) == NULL) {
+		if (opt_prof && (cnt = prof_alloc_prep(size)) == NULL) {
 			result = NULL;
 			ret = EINVAL;
 		} else
@@ -1030,7 +1039,7 @@ JEMALLOC_P(calloc)(size_t num, size_t size)
 	}
 
 #ifdef JEMALLOC_PROF
-	if (opt_prof && (cnt = prof_alloc_prep()) == NULL) {
+	if (opt_prof && (cnt = prof_alloc_prep(num_size)) == NULL) {
 		ret = NULL;
 		goto RETURN;
 	}
@@ -1106,7 +1115,7 @@ JEMALLOC_P(realloc)(void *ptr, size_t size)
 		if (opt_prof) {
 			old_size = isalloc(ptr);
 			old_cnt = prof_cnt_get(ptr);
-			if ((cnt = prof_alloc_prep()) == NULL) {
+			if ((cnt = prof_alloc_prep(size)) == NULL) {
 				ret = NULL;
 				goto OOM;
 			}
@@ -1144,7 +1153,7 @@ OOM:
 			ret = NULL;
 		} else {
 #ifdef JEMALLOC_PROF
-			if (opt_prof && (cnt = prof_alloc_prep()) == NULL) {
+			if (opt_prof && (cnt = prof_alloc_prep(size)) == NULL) {
 				ret = NULL;
 			} else
 #endif

jemalloc/src/prof.c

@@ -12,11 +12,14 @@
 #include <libunwind.h>
 #endif
 
+#include <math.h>
+
 /******************************************************************************/
 /* Data. */
 
 bool		opt_prof = false;
-size_t		opt_lg_prof_bt_max = 2;
+size_t		opt_lg_prof_bt_max = LG_PROF_BT_MAX_DEFAULT;
+size_t		opt_lg_prof_sample = LG_PROF_SAMPLE_DEFAULT;
 size_t		opt_lg_prof_interval = LG_PROF_INTERVAL_DEFAULT;
 bool		opt_prof_udump = false;
 bool		opt_prof_leak = false;
@@ -52,6 +55,13 @@ static pthread_key_t	bt2cnt_tsd;
 /* (1U << opt_lg_prof_bt_max). */
 static unsigned		prof_bt_max;
 
+static __thread uint64_t prof_sample_prn_state
+    JEMALLOC_ATTR(tls_model("initial-exec"));
+static __thread uint64_t prof_sample_threshold
+    JEMALLOC_ATTR(tls_model("initial-exec"));
+static __thread uint64_t prof_sample_accum
+    JEMALLOC_ATTR(tls_model("initial-exec"));
+
 static malloc_mutex_t	prof_dump_seq_mtx;
 static uint64_t		prof_dump_seq;
 static uint64_t		prof_dump_iseq;
@@ -500,15 +510,27 @@ prof_lookup(prof_bt_t *bt)
 }
 
 prof_thr_cnt_t *
-prof_alloc_prep(void)
+prof_alloc_prep(size_t size)
 {
 	prof_thr_cnt_t *ret;
 	void *vec[prof_bt_max];
 	prof_bt_t bt;
 
+	/*
+	 * Determine whether to capture a backtrace based on whether size is
+	 * enough for prof_accum to reach prof_sample_threshold.  However,
+	 * delay updating these variables until prof_{m,re}alloc(), because we
+	 * don't know for sure that the allocation will succeed.
+	 *
+	 * Use subtraction rather than addition to avoid potential integer
+	 * overflow.
+	 */
+	if (size >= prof_sample_threshold - prof_sample_accum) {
 		bt_init(&bt, vec);
 		prof_backtrace(&bt, 2, prof_bt_max);
 		ret = prof_lookup(&bt);
+	} else
+		ret = (prof_thr_cnt_t *)(uintptr_t)1U;
 
 	return (ret);
 }
@@ -550,13 +572,68 @@ prof_cnt_set(const void *ptr, prof_thr_cnt_t *cnt)
 		huge_prof_cnt_set(ptr, cnt);
 }
 
+static inline void
+prof_sample_threshold_update(void)
+{
+	uint64_t r;
+	double u;
+
+	/*
+	 * Compute prof_sample_threshold as a geometrically distributed random
+	 * variable with mean (2^opt_lg_prof_sample).
+	 */
+	prn64(r, 53, prof_sample_prn_state, (uint64_t)1125899906842625LLU,
+	    1058392653243283975);
+	u = (double)r * (1.0/9007199254740992.0L);
+	prof_sample_threshold = (uint64_t)(log(u) /
+	    log(1.0 - (1.0 / (double)((uint64_t)1U << opt_lg_prof_sample))))
+	    + (uint64_t)1U;
+}
+
+static inline void
+prof_sample_accum_update(size_t size)
+{
+
+	if (opt_lg_prof_sample == 0) {
+		/*
+		 * Don't bother with sampling logic, since sampling interval is
+		 * 1.
+		 */
+		return;
+	}
+
+	if (prof_sample_threshold == 0) {
+		/* Initialize.  Seed the prng differently for each thread. */
+		prof_sample_prn_state = (uint64_t)(uintptr_t)&size;
+		prof_sample_threshold_update();
+	}
+
+	/* Take care to avoid integer overflow. */
+	if (size >= prof_sample_threshold - prof_sample_accum) {
+		prof_sample_accum -= (prof_sample_threshold - size);
+		/*
+		 * Compute new geometrically distributed prof_sample_threshold.
+		 */
+		prof_sample_threshold_update();
+		while (prof_sample_accum >= prof_sample_threshold) {
+			prof_sample_accum -= prof_sample_threshold;
+			prof_sample_threshold_update();
+		}
+	} else
+		prof_sample_accum += size;
+}
+
 void
 prof_malloc(const void *ptr, prof_thr_cnt_t *cnt)
 {
 	size_t size = isalloc(ptr);
 
-	prof_cnt_set(ptr, cnt);
+	assert(ptr != NULL);
 
+	prof_cnt_set(ptr, cnt);
+	prof_sample_accum_update(size);
+
+	if ((uintptr_t)cnt > (uintptr_t)1U) {
 		cnt->epoch++;
 		/*********/
 		mb_write();
@@ -572,6 +649,7 @@ prof_malloc(const void *ptr, prof_thr_cnt_t *cnt)
 		/*********/
 		mb_write();
 		/*********/
+	}
 }
 
 void
@@ -580,20 +658,23 @@ prof_realloc(const void *ptr, prof_thr_cnt_t *cnt, const void *old_ptr,
 {
 	size_t size = isalloc(ptr);
 
+	if (ptr != NULL) {
 		prof_cnt_set(ptr, cnt);
+		prof_sample_accum_update(size);
+	}
 
-	if (old_cnt != NULL)
+	if ((uintptr_t)old_cnt > (uintptr_t)1U)
 		old_cnt->epoch++;
-	if (cnt != NULL)
+	if ((uintptr_t)cnt > (uintptr_t)1U)
 		cnt->epoch++;
 	/*********/
 	mb_write();
 	/*********/
-	if (old_cnt != NULL) {
+	if ((uintptr_t)old_cnt > (uintptr_t)1U) {
 		old_cnt->cnts.curobjs--;
 		old_cnt->cnts.curbytes -= old_size;
 	}
-	if (cnt != NULL) {
+	if ((uintptr_t)cnt > (uintptr_t)1U) {
 		cnt->cnts.curobjs++;
 		cnt->cnts.curbytes += size;
 		cnt->cnts.accumobjs++;
@@ -602,9 +683,9 @@ prof_realloc(const void *ptr, prof_thr_cnt_t *cnt, const void *old_ptr,
 	/*********/
 	mb_write();
 	/*********/
-	if (old_cnt != NULL)
+	if ((uintptr_t)old_cnt > (uintptr_t)1U)
 		old_cnt->epoch++;
-	if (cnt != NULL)
+	if ((uintptr_t)cnt > (uintptr_t)1U)
 		cnt->epoch++;
 	/*********/
 	mb_write(); /* Not strictly necessary. */
@@ -614,6 +695,8 @@ void
 prof_free(const void *ptr)
 {
 	prof_thr_cnt_t *cnt = prof_cnt_get(ptr);
+
+	if ((uintptr_t)cnt > (uintptr_t)1) {
 		size_t size = isalloc(ptr);
 
 		cnt->epoch++;
@@ -629,6 +712,7 @@ prof_free(const void *ptr)
 		/*********/
 		mb_write();
 		/*********/
+	}
 }
 
 static void
@@ -825,7 +909,13 @@ prof_dump(const char *filename, bool leakcheck)
 	prof_write(umax2s(cnt_all.accumobjs, 10, buf));
 	prof_write(": ");
 	prof_write(umax2s(cnt_all.accumbytes, 10, buf));
+	if (opt_lg_prof_sample == 0)
 		prof_write("] @ heapprofile\n");
+	else {
+		prof_write("] @ heap_v2/");
+		prof_write(umax2s((uint64_t)1U << opt_lg_prof_sample, 10, buf));
+		prof_write("\n");
+	}
 
 	/* Dump  per ctx profile stats. */
 	for (tabind = 0; ckh_iter(&bt2ctx, &tabind, (void **)&bt, (void **)&ctx)
@@ -1104,6 +1194,14 @@ prof_boot0(void)
 	 * initialized, so this function must be executed early.
 	 */
 
+	if (opt_lg_prof_sample > 0) {
+		/*
+		 * Disable leak checking, since not all allocations will be
+		 * sampled.
+		 */
+		opt_prof_leak = false;
+	}
+
 	if (opt_prof_leak && opt_prof == false) {
 		/*
 		 * Enable opt_prof, but in such a way that profiles are never

jemalloc/src/stats.c

@@ -540,13 +540,18 @@ stats_print(void (*write4)(void *, const char *, const char *, const char *,
 			    tcache_nslots && ssv >= 0 ? umax2s(tcache_gc_sweep,
 			    10, s) : "N/A", "\n", "");
 		}
-		if ((err = JEMALLOC_P(mallctl)("opt.lg_prof_bt_max", &sv, &ssz,
+		if ((err = JEMALLOC_P(mallctl)("opt.prof", &bv, &bsz, NULL, 0))
-		    NULL, 0)) == 0) {
+		   == 0 && bv) {
+			xmallctl("opt.lg_prof_bt_max", &sv, &ssz, NULL, 0);
 			write4(w4opaque, "Maximum profile backtrace depth: ",
 			    umax2s((1U << sv), 10, s), "\n", "");
-		}
+
-		if ((err = JEMALLOC_P(mallctl)("opt.lg_prof_interval", &sv,
+			xmallctl("opt.lg_prof_sample", &sv, &ssz, NULL, 0);
-		    &ssz, NULL, 0)) == 0) {
+			write4(w4opaque, "Average profile sample interval: ",
+			    umax2s((1U << sv), 10, s), "", "");
+			write4(w4opaque, " (2^", umax2s(sv, 10, s), ")\n", "");
+
+			xmallctl("opt.lg_prof_interval", &sv, &ssz, NULL, 0);
 			write4(w4opaque, "Average profile dump interval: ",
 			    umax2s((1U << sv), 10, s), "", "");
 			write4(w4opaque, " (2^", umax2s(sv, 10, s), ")\n", "");