From: Michael Tremer <michael.tremer@ipfire.org>
Date: Wed, 22 Oct 2025 20:28:01 +0000 (+0000)
Subject: metrics: Only require one allocation
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6a47bd6dad0ceb128beb248bf5270e737a4045c5;p=telemetry.git

metrics: Only require one allocation

Since we know how many metrics we might expect from the beginning we can
realise the metrics as a variable array and only have one allocation.

Since this application is having a lot of allocations, this would quite
save a bit of memory fragmentation and load on the allocator.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
---

diff --git a/src/daemon/metrics.c b/src/daemon/metrics.c
index e61ff68..79e9016 100644
--- a/src/daemon/metrics.c
+++ b/src/daemon/metrics.c
@@ -65,8 +65,8 @@ struct td_metrics {
 	struct timeval t;
 
 	// Metrics
-	td_metric* metrics;
 	unsigned int num_metrics;
+	td_metric metrics[];
 };
 
 static int td_metrics_valid_object(td_metrics* self, const char* object) {
@@ -113,17 +113,19 @@ static void td_metrics_free(td_metrics* self) {
 		td_source_unref(self->source);
 	if (self->ctx)
 		td_ctx_unref(self->ctx);
-	if (self->metrics)
-		free(self->metrics);
 	free(self);
 }
 
 int td_metrics_create(td_metrics** metrics, td_ctx* ctx, td_source* source, const char* object) {
+	unsigned int num_metrics = 0;
 	td_metrics* self = NULL;
 	int r;
 
+	// Fetch how many data sources there are
+	num_metrics = td_source_num_data_sources(source);
+
 	// Allocate some memory
-	self = calloc(1, sizeof(*self));
+	self = calloc(1, sizeof(*self) + (num_metrics * sizeof(*self->metrics)));
 	if (!self)
 		return -errno;
 
@@ -150,6 +152,9 @@ int td_metrics_create(td_metrics** metrics, td_ctx* ctx, td_source* source, cons
 		}
 	}
 
+	// Store the number of data sources
+	self->num_metrics = num_metrics;
+
 	// Fetch the current time
 	r = gettimeofday(&self->t, NULL);
 	if (r < 0) {
@@ -157,24 +162,6 @@ int td_metrics_create(td_metrics** metrics, td_ctx* ctx, td_source* source, cons
 		goto ERROR;
 	}
 
-	// Fetch the number of data sources
-	self->num_metrics = td_source_num_data_sources(self->source);
-
-	// Fail if there are no data sources
-	if (!self->num_metrics) {
-		ERROR(self->ctx, "Source %s has no data sources\n", td_source_name(self->source));
-		r = -EINVAL;
-		goto ERROR;
-	}
-
-	// Allocate space for the metrics
-	self->metrics = calloc(self->num_metrics, sizeof(*self->metrics));
-	if (!self->metrics) {
-		ERROR(self->ctx, "Failed to allocate %u metric(s): %m\n", self->num_metrics);
-		r = -errno;
-		goto ERROR;
-	}
-
 	// Return the pointer
 	*metrics = self;
 	return 0;