trace: don't use randombytes_buf(), use pseudorand.

This is much faster to give 64 bits of data, and we don't need
cryptographic randomness.

This brings us back to 413ns per trace.

Before:
	real	0m5.819000-6.472000(6.2064+/-0.26)s
	user	0m3.779000-4.101000(3.956+/-0.12)s
	sys	0m2.040000-2.431000(2.2496+/-0.15)s

After:
	real	0m3.981000-4.247000(4.1276+/-0.11)s
	user	0m3.979000-4.245000(4.126+/-0.11)s
	sys	0m0.000000-0.002000(0.001+/-0.00063)s

Signed-off-by: Rusty Russell <[email protected]>
Changelog-Fixed: lightingd: trimmed overhead of tracing infrastructure.

Author: rustyrussell

common/test/Makefile

@@ -118,6 +118,7 @@ common/test/run-splice_script:				\
 common/test/run-trace:					\
 	common/amount.o                                 \
 	common/memleak.o				\
+	common/pseudorand.o				\
 	common/trace.o					\
 	wire/fromwire.o					\
 	wire/towire.o

common/trace.c

@@ -1,13 +1,14 @@
 #include "config.h"
 #include <assert.h>
+#include <ccan/endian/endian.h>
 #include <ccan/htable/htable.h>
 #include <ccan/str/hex/hex.h>
 #include <ccan/tal/tal.h>
 #include <ccan/time/time.h>
 #include <common/json_stream.h>
 #include <common/memleak.h>
+#include <common/pseudorand.h>
 #include <common/trace.h>
-#include <sodium/randombytes.h>
 #include <stdio.h>
 #include <unistd.h>
 
@@ -16,9 +17,6 @@
 
 #define MAX_ACTIVE_SPANS 128
 
-#define HEX_SPAN_ID_SIZE (2*SPAN_ID_SIZE+1)
-#define HEX_TRACE_ID_SIZE (2 * TRACE_ID_SIZE + 1)
-
 /* The traceperent format is defined in W3C Trace Context RFC[1].
  * Its format is defined as
  *
@@ -52,13 +50,13 @@ struct span_tag {
 
 struct span {
 	/* Our own id */
-	u8 id[SPAN_ID_SIZE];
+	u64 id;
 
 	/* 0 if we have no parent. */
-	u8 parent_id[SPAN_ID_SIZE];
+	u64 parent_id;
 
 	/* The trace_id for this span and all its children. */
-	u8 trace_id[TRACE_ID_SIZE];
+	u64 trace_id_hi, trace_id_lo;
 
 	u64 start_time;
 	u64 end_time;
@@ -88,7 +86,9 @@ static struct span *current;
  * own parent. */
 static void trace_inject_traceparent(void)
 {
-	char *traceparent;
+	const char *traceparent;
+	be64 trace_hi, trace_lo, span;
+
 	traceparent = getenv("CLN_TRACEPARENT");
 	if (!traceparent)
 		return;
@@ -97,13 +97,17 @@ static void trace_inject_traceparent(void)
 	trace_span_start("", active_spans);
 	current->remote = true;
 	assert(current && !current->parent);
-	if (!hex_decode(traceparent + 3, 2*TRACE_ID_SIZE, current->trace_id,
-			TRACE_ID_SIZE) ||
-	    !hex_decode(traceparent + 36, 2*SPAN_ID_SIZE, current->id,
-			SPAN_ID_SIZE)) {
+
+	if (!hex_decode(traceparent + 3, 16, &trace_hi, sizeof(trace_hi))
+	    || !hex_decode(traceparent + 3 + 16, 16, &trace_lo, sizeof(trace_lo))
+	    || !hex_decode(traceparent + 3 + 16 + 16 + 1, 16, &span, sizeof(span))) {
 		/* We failed to parse the traceparent, abandon. */
 		fprintf(stderr, "Failed!");
 		trace_span_end(active_spans);
+	} else {
+		current->trace_id_hi = be64_to_cpu(trace_hi);
+		current->trace_id_lo = be64_to_cpu(trace_lo);
+		current->id = be64_to_cpu(span);
 	}
 }
 
@@ -217,9 +221,7 @@ static struct span *trace_span_slot(void)
 
 static void trace_emit(struct span *s)
 {
-	char span_id[HEX_SPAN_ID_SIZE];
-	char trace_id[HEX_TRACE_ID_SIZE];
-	char parent_span_id[HEX_SPAN_ID_SIZE];
+	char span_id[hex_str_size(sizeof(s->id))];
 	char buffer[MAX_BUF_SIZE + 1];
 	size_t len;
 
@@ -229,12 +231,7 @@ static void trace_emit(struct span *s)
 	if (s->remote)
 		return;
 
-	hex_encode(s->id, SPAN_ID_SIZE, span_id, HEX_SPAN_ID_SIZE);
-	hex_encode(s->trace_id, TRACE_ID_SIZE, trace_id, HEX_TRACE_ID_SIZE);
-
-	if (s->parent)
-		hex_encode(s->parent_id, SPAN_ID_SIZE, parent_span_id, HEX_SPAN_ID_SIZE);
-
+	sprintf(span_id, "%016"PRIx64, s->id);
 	len = snprintf(buffer, MAX_BUF_SIZE,
 		       "[{\"id\": \"%s\", \"name\": \"%s\", "
 		       "\"timestamp\": %" PRIu64 ", \"duration\": %" PRIu64 ","
@@ -243,8 +240,8 @@ static void trace_emit(struct span *s)
 
 	if (s->parent != NULL) {
 		len += snprintf(buffer + len, MAX_BUF_SIZE - len,
-				"\"parentId\": \"%s\",",
-				parent_span_id);
+				"\"parentId\": \"%016"PRIx64"\",",
+				s->parent_id);
 		if (len > MAX_BUF_SIZE)
 			len = MAX_BUF_SIZE;
 	}
@@ -265,10 +262,12 @@ static void trace_emit(struct span *s)
 			len = MAX_BUF_SIZE;
 	}
 	len += snprintf(buffer + len, MAX_BUF_SIZE - len,
-			"}, \"traceId\": \"%s\"}]", trace_id);
+			"}, \"traceId\": \"%016"PRIx64"%016"PRIx64"\"}]",
+			s->trace_id_hi, s->trace_id_lo);
 	if (len > MAX_BUF_SIZE)
 		len = MAX_BUF_SIZE;
 	buffer[len] = '\0';
+	/* FIXME: span_id here is in hex, could be u64? */
 	DTRACE_PROBE2(lightningd, span_emit, span_id, buffer);
 }
 
@@ -277,14 +276,7 @@ static void trace_emit(struct span *s)
  */
 static void trace_span_clear(struct span *s)
 {
-	s->key = 0;
-	memset(s->id, 0, SPAN_ID_SIZE);
-	memset(s->trace_id, 0, TRACE_ID_SIZE);
-
-	s->parent = NULL;
-	s->name = NULL;
-	for (size_t i = 0; i < SPAN_MAX_TAGS; i++)
-		s->tags[i].name = NULL;
+	memset(s, 0, sizeof(*s));
 }
 
 void trace_span_start_(const char *name, const void *key)
@@ -302,26 +294,28 @@ void trace_span_start_(const char *name, const void *key)
 	if (!s)
 		return;
 	s->key = numkey;
-	randombytes_buf(s->id, SPAN_ID_SIZE);
+	s->id = pseudorand_u64();
 	s->start_time = (now.ts.tv_sec * 1000000) + now.ts.tv_nsec / 1000;
 	s->parent = current;
 	s->name = name;
 
 	/* If this is a new root span we also need to associate a new
 	 * trace_id with it. */
 	if (!current) {
-		randombytes_buf(s->trace_id, TRACE_ID_SIZE);
+		s->trace_id_hi = pseudorand_u64();
+		s->trace_id_lo = pseudorand_u64();
 	} else {
-		memcpy(s->parent_id, current->id, SPAN_ID_SIZE);
-		memcpy(s->trace_id, current->trace_id, TRACE_ID_SIZE);
+		s->parent_id = current->id;
+		s->trace_id_hi = current->trace_id_hi;
+		s->trace_id_lo = current->trace_id_lo;
 	}
 
 	current = s;
 	trace_check_tree();
 	DTRACE_PROBE1(lightningd, span_start, s->id);
 }
 
-void trace_span_remote(u8 trace_id[TRACE_ID_SIZE], u8 span_id[SPAN_ID_SIZE])
+void trace_span_remote(u64 trace_id_hi, u64 trade_id_lo, u64 span_id)
 {
 	abort();
 }

common/trace.h

@@ -3,8 +3,6 @@
 #include "config.h"
 #include <ccan/short_types/short_types.h>
 
-#define SPAN_ID_SIZE 8
-#define TRACE_ID_SIZE 16
 #undef TRACE_DEBUG
 
 /* name must be a string constant */
@@ -13,7 +11,7 @@ void trace_span_start_(const char *name, const void *key);
 void trace_span_end(const void *key);
 void trace_span_tag(const void *key, const char *name, const char *value);
 void trace_cleanup(void);
-void trace_span_remote(u8 trace_id[TRACE_ID_SIZE], u8 span_id[SPAN_ID_SIZE]);
+void trace_span_remote(u64 trace_id_hi, u64 trade_id_lo, u64 span_id);
 
 #define TRACE_LBL __FILE__ ":" stringify(__LINE__)
 void trace_span_suspend_(const void *key, const char *lbl);

plugins/bkpr/test/run-bkpr_db.c

@@ -219,6 +219,9 @@ bool param_check(struct command *cmd UNNEEDED,
 		 const char *buffer UNNEEDED,
 		 const jsmntok_t tokens[] UNNEEDED, ...)
 { fprintf(stderr, "param_check called!\n"); abort(); }
+/* Generated stub for pseudorand_u64 */
+uint64_t pseudorand_u64(void)
+{ fprintf(stderr, "pseudorand_u64 called!\n"); abort(); }
 /* Generated stub for toks_alloc */
 jsmntok_t *toks_alloc(const tal_t *ctx UNNEEDED)
 { fprintf(stderr, "toks_alloc called!\n"); abort(); }

plugins/bkpr/test/run-recorder.c

@@ -225,6 +225,9 @@ bool param_check(struct command *cmd UNNEEDED,
 		 const char *buffer UNNEEDED,
 		 const jsmntok_t tokens[] UNNEEDED, ...)
 { fprintf(stderr, "param_check called!\n"); abort(); }
+/* Generated stub for pseudorand_u64 */
+uint64_t pseudorand_u64(void)
+{ fprintf(stderr, "pseudorand_u64 called!\n"); abort(); }
 /* Generated stub for toks_alloc */
 jsmntok_t *toks_alloc(const tal_t *ctx UNNEEDED)
 { fprintf(stderr, "toks_alloc called!\n"); abort(); }