JSON profiler reports

This introduces a JSON output format for cost-centre profiler reports.
It's not clear whether this is really something we want to introduce
given that we may also move to a more Haskell-driven output pipeline in
the future, but I nevertheless found this helpful, so I thought I would
put it up.

Test Plan: Compile a program with `-prof -fprof-auto`; run with `+RTS
-pj`

Reviewers: austin, erikd, simonmar

Reviewed By: simonmar

Subscribers: duncan, maoe, thomie, simonmar

Differential Revision: https://phabricator.haskell.org/D3132

1 files changed, 127 insertions, 0 deletions

diff --git a/rts/ProfilerReportJson.c b/rts/ProfilerReportJson.c
new file mode 100644
index 0000000000..b4c77042d7
--- /dev/null
+++ b/rts/ProfilerReportJson.c
@@ -0,0 +1,127 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team, 1998-2017
+ *
+ * Generating cost-centre profiler JSON report
+ *
+ * ---------------------------------------------------------------------------*/
+
+#ifdef PROFILING
+
+#include "PosixSource.h"
+#include "Rts.h"
+
+#include "RtsUtils.h"
+#include "ProfilerReportJson.h"
+#include "Profiling.h"
+
+// This only handles characters that you might see in a Haskell cost-centre
+// name.
+static void escapeString(char const* str, char *out, int len)
+{
+    len--; // reserve character in output for terminating NUL
+    for (; str != '\0' && len > 0; str++) {
+        char c = *str;
+        if (c == '\\') {
+            if (len < 2) break;
+            *out = '\\'; out++; len--;
+            *out = '\\'; out++; len--;
+        } else if (c == '\n') {
+            if (len < 2) break;
+            *out = '\\'; out++; len--;
+            *out = 'n';  out++; len--;
+        } else {
+            *out = c; out++; len--;
+        }
+    }
+    *out = '\0';
+}
+
+static void
+logCostCentres(FILE *prof_file)
+{
+    char tmp[256];
+    bool needs_comma = false;
+    fprintf(prof_file, "[\n");
+    for (CostCentre *cc = CC_LIST; cc != NULL; cc = cc->link) {
+        escapeString(cc->label, tmp, sizeof(tmp));
+        fprintf(prof_file,
+                "%s"
+                "{\"id\": %" FMT_Int ", "
+                "\"label\": \"%s\", "
+                "\"module\": \"%s\", "
+                "\"src_loc\": \"%s\", "
+                "\"is_caf\": %s}",
+                needs_comma ? ", " : "",
+                cc->ccID, tmp, cc->module, cc->srcloc,
+                cc->is_caf ? "true" : "false");
+        needs_comma = true;
+    }
+    fprintf(prof_file, "]\n");
+}
+
+static void
+logCostCentreStack(FILE *prof_file, CostCentreStack const *ccs)
+{
+    fprintf(prof_file,
+            "{\"id\": %" FMT_Int ", "
+            "\"entries\": %" FMT_Word64 ", "
+            "\"alloc\": %" FMT_Word ", "
+            "\"ticks\": %" FMT_Word ", ",
+            ccs->cc->ccID,
+            ccs->scc_count,
+            ccs->mem_alloc * sizeof(W_),
+            ccs->time_ticks);
+
+    bool need_comma = false;
+    fprintf(prof_file, "\"children\": [");
+    for (IndexTable *i = ccs->indexTable; i != 0; i = i->next) {
+        if (!i->back_edge) {
+            if (need_comma) {
+                fprintf(prof_file, ",");
+            }
+            logCostCentreStack(prof_file, i->ccs);
+            need_comma = true;
+        }
+    }
+    fprintf(prof_file, "]}\n");
+}
+
+void
+writeCCSReportJson(FILE *prof_file,
+                   CostCentreStack const *stack,
+                   ProfilerTotals totals)
+{
+    fprintf(prof_file, "{\n\"program\": \"%s\",\n", prog_name);
+    fprintf(prof_file, "\"arguments\": [");
+    for (int count = 0; prog_argv[count]; count++)
+        fprintf(prof_file, "%s\"%s\"",
+                count == 0 ? "" : ", ", prog_argv[count]);
+    fprintf(prof_file, "],\n\"rts_arguments\": [");
+    for (int count = 0; rts_argv[count]; count++)
+        fprintf(prof_file, "%s\"%s\"",
+                count == 0 ? "" : ", ", rts_argv[count]);
+    fprintf(prof_file, "],\n");
+
+    fprintf(prof_file, "\"end_time\": \"%s\",\n", time_str());
+    fprintf(prof_file, "\"initial_capabilities\": %d,\n",
+            RtsFlags.ParFlags.nCapabilities);
+    fprintf(prof_file, "\"total_time\": %11.2f,\n",
+            ((double) totals.total_prof_ticks *
+             (double) RtsFlags.MiscFlags.tickInterval) / (TIME_RESOLUTION * n_capabilities));
+    fprintf(prof_file, "\"total_ticks\": %lu,\n",
+            (unsigned long) totals.total_prof_ticks);
+    fprintf(prof_file, "\"tick_interval\": %d,\n",
+            (int) TimeToUS(RtsFlags.MiscFlags.tickInterval));
+    fprintf(prof_file, "\"total_alloc\":%" FMT_Word64 ",\n",
+            totals.total_alloc * sizeof(W_));
+
+    fprintf(prof_file, "\"cost_centres\": ");
+    logCostCentres(prof_file);
+    fprintf(prof_file, ",\n\"profile\": ");
+    logCostCentreStack(prof_file, stack);
+    fprintf(prof_file, "}\n");
+}
+
+
+#endif /* PROFILING */