Initial

1 files changed, 176 insertions, 0 deletions

diff --git a/cbits/hook.c b/cbits/hook.c
new file mode 100644
index 0000000..e05ccd4
--- /dev/null
+++ b/cbits/hook.c
@@ -0,0 +1,176 @@
+#include "Rts.h"
+#include <string.h>
+
+// needs C11
+#include <threads.h>
+
+static size_t min_sz(size_t a, size_t b) {
+	return a < b ? a : b;
+}
+
+extern RtsConfig rtsConfig;
+
+// A copy of GCDetails_ with known structure that can be depended on by the Haskell code.
+struct ShadowDetails {
+	// The generation number of this GC
+	uint32_t gen;
+	// Number of threads used in this GC
+	uint32_t threads;
+	// Number of bytes allocated since the previous GC
+	uint64_t allocated_bytes;
+	// Total amount of live data in the heap (incliudes large + compact data).
+	// Updated after every GC. Data in uncollected generations (in minor GCs)
+	// are considered live.
+	uint64_t live_bytes;
+	// Total amount of live data in large objects
+	uint64_t large_objects_bytes;
+	// Total amount of live data in compact regions
+	uint64_t compact_bytes;
+	// Total amount of slop (wasted memory)
+	uint64_t slop_bytes;
+	// Total amount of memory in use by the RTS
+	uint64_t mem_in_use_bytes;
+	// Total amount of data copied during this GC
+	uint64_t copied_bytes;
+	// In parallel GC, the max amount of data copied by any one thread
+	uint64_t par_max_copied_bytes;
+	// In parallel GC, the amount of balanced data copied by all threads
+	uint64_t par_balanced_copied_bytes;
+	// The time elapsed during synchronisation before GC
+	// NOTE: nanoseconds!
+	uint64_t sync_elapsed_ns;
+	// The CPU time used during GC itself
+	// NOTE: nanoseconds!
+	uint64_t cpu_ns;
+	// The time elapsed during GC itself
+	// NOTE: nanoseconds!
+	uint64_t elapsed_ns;
+
+	// Concurrent garbage collector
+
+	// The CPU time used during the post-mark pause phase of the concurrent
+	// nonmoving GC.
+	// NOTE: nanoseconds!
+	uint64_t nonmoving_gc_sync_cpu_ns;
+	// The time elapsed during the post-mark pause phase of the concurrent
+	// nonmoving GC.
+	// NOTE: nanoseconds!
+	uint64_t nonmoving_gc_sync_elapsed_ns;
+	// The CPU time used during the post-mark pause phase of the concurrent
+	// nonmoving GC.
+	// NOTE: nanoseconds!
+	uint64_t nonmoving_gc_cpu_ns;
+	// The time elapsed during the post-mark pause phase of the concurrent
+	// nonmoving GC.
+	// NOTE: nanoseconds!
+	uint64_t nonmoving_gc_elapsed_ns;
+};
+
+static void shadow_copy(struct ShadowDetails *dst, const struct GCDetails_ *src) {
+#define COPY(field) dst->field = src->field;
+#define COPYTIME(field) dst->field = TimeToNS(src->field);
+	COPY(gen);
+	COPY(threads);
+	COPY(allocated_bytes);
+	COPY(live_bytes);
+	COPY(large_objects_bytes);
+	COPY(compact_bytes);
+	COPY(slop_bytes);
+	COPY(mem_in_use_bytes);
+	COPY(copied_bytes);
+	COPY(par_max_copied_bytes);
+	COPY(par_balanced_copied_bytes);
+	COPYTIME(sync_elapsed_ns);
+	COPYTIME(cpu_ns);
+	COPYTIME(elapsed_ns);
+
+	COPYTIME(nonmoving_gc_sync_cpu_ns);
+	COPYTIME(nonmoving_gc_sync_elapsed_ns);
+	COPYTIME(nonmoving_gc_cpu_ns);
+	COPYTIME(nonmoving_gc_elapsed_ns);
+#undef COPY
+#undef COPYTIME
+}
+
+// --------
+// GLOBAL VARIABLES
+// --------
+
+static void (*old_hook)(const struct GCDetails_ *details) = NULL;
+static mtx_t detlog_mutex;
+static size_t detlog_capacity = 0, detlog_length = 0;
+static struct ShadowDetails *detlog = NULL;
+
+// --------
+// END OF GLOBAL VARIABLES
+// --------
+
+static void hook_callback(const struct GCDetails_ *details) {
+	static bool alloc_failed = false;
+
+	if (alloc_failed) goto cleanup_no_mutex;
+
+	if (mtx_lock(&detlog_mutex) != thrd_success) {
+		fprintf(stderr, "ghc-gc-hook: ERROR: Mutex lock failed\n");
+		alloc_failed = true;  // dumb proxy for "don't do anything anymore please"
+		goto cleanup_no_mutex;
+	}
+
+	// mutex is locked from here
+
+	if (detlog_length == detlog_capacity) {
+		detlog_capacity = detlog_capacity == 0 ? 128 : 2 * detlog_capacity;
+		detlog = realloc(detlog, detlog_capacity * sizeof(detlog[0]));
+		if (detlog == NULL || detlog_capacity == 0) {  // also check for overflow here
+			fprintf(stderr, "ghc-gc-hook: ERROR: Could not allocate memory for GC log hook\n");
+			alloc_failed = true;
+			goto cleanup;
+		}
+	}
+
+	shadow_copy(&detlog[detlog_length], details);
+	detlog_length++;
+
+cleanup:
+	mtx_unlock(&detlog_mutex);  // ignore return value
+
+cleanup_no_mutex:
+	if (old_hook) old_hook(details);
+}
+
+// --------
+// EXPORTED FUNCTIONS
+// --------
+
+void copy_log_to_buffer(size_t space_available, char *buffer, size_t *unit_size, size_t *num_stored) {
+	if (mtx_lock(&detlog_mutex) != thrd_success) {
+		fprintf(stderr, "ghc-gc-hook: ERROR: Mutex lock failed\n");
+		*unit_size = 0;
+		*num_stored = 0;
+		return;
+	}
+
+	const size_t sz = sizeof(detlog[0]);
+	const size_t n = min_sz(space_available / sz, detlog_length);
+
+	// First copy over the fitting items
+	memcpy(buffer, detlog, n * sz);
+	*unit_size = sz;
+	*num_stored = n;
+
+	// Then shift back the remaining items
+	memmove(detlog, detlog + n, (detlog_length - n) * sizeof(detlog[0]));
+	detlog_length -= n;
+
+	mtx_unlock(&detlog_mutex);
+}
+
+void set_gchook() {
+	if (mtx_init(&detlog_mutex, mtx_plain) != thrd_success) {
+		fprintf(stderr, "ghc-gc-hook: ERROR: Mutex initialisation failed\n");
+		return;
+	}
+
+	old_hook = rtsConfig.gcDoneHook;
+	rtsConfig.gcDoneHook = hook_callback;
+}