ircd::ios: Add epoch history in circular buffer for profiling w/ console cmd.

include/ircd/ios.h

@@ -108,7 +108,9 @@ struct ircd::ios::descriptor
 	std::unique_ptr<struct stats> stats;
 	std::function<void *(handler &, const size_t &)> allocator;
 	std::function<void (handler &, void *const &, const size_t &)> deallocator;
-	bool continuation;
+	std::vector<std::array<uint64_t, 2>> history; // epoch, cycles
+	uint8_t history_pos {0};
+	bool continuation {false};
 
 	descriptor(const string_view &name,
 	           const decltype(allocator) & = default_allocator,

ircd/ios.cc

@@ -100,6 +100,14 @@ ircd::ios::descriptor::descriptor(const string_view &name,
 {
 	deallocator?: default_deallocator
 }
+,history_pos
+{
+	0
+}
+,history
+(
+	256, {0}
+)
 ,continuation
 {
 	continuation
@@ -169,6 +177,11 @@ ircd::ios::descriptor::stats::operator+=(const stats &o)
 // handler
 //
 
+namespace ircd::ios
+{
+	constexpr bool profile_history {false};
+}
+
 decltype(ircd::ios::handler::current)
 thread_local
 ircd::ios::handler::current;
@@ -226,6 +239,14 @@ noexcept
 	stats.slice_last = slice_stop - handler->ts;
 	stats.slice_total += stats.slice_last;
 
+	if constexpr(profile_history)
+	{
+		assert(descriptor.history_pos < descriptor.history.size());
+		descriptor.history[descriptor.history_pos][0] = handler::epoch;
+		descriptor.history[descriptor.history_pos][1] = stats.slice_last;
+		++descriptor.history_pos;
+	}
+
 	assert(handler::current == handler);
 	handler::current = nullptr;
 }
@@ -236,14 +257,14 @@ ircd::ios::handler::enter(handler *const &handler)
 noexcept
 {
 	assert(!handler::current);
+	handler::current = handler;
+	++handler::epoch;
+
 	assert(handler && handler->descriptor);
 	auto &descriptor(*handler->descriptor);
 
 	assert(descriptor.stats);
 	auto &stats(*descriptor.stats);
-
-	handler::current = handler;
-	++handler::epoch;
 	++stats.calls;
 
 	const auto last_ts

modules/console.cc

@@ -1663,6 +1663,115 @@ console_cmd__ios(opt &out, const string_view &line)
 	return true;
 }
 
+bool
+console_cmd__ios__record(opt &out, const string_view &line)
+{
+	std::map<uint64_t, std::tuple<uint64_t, const ios::descriptor *>> map;
+	for(const auto *const &descriptor : ios::descriptor::list)
+	{
+		assert(descriptor);
+		const auto &d(*descriptor);
+
+		const auto &history(d.history);
+		const auto &pos(d.history_pos);
+
+		for(size_t i(pos); i < 256; ++i)
+		{
+			if(!history[i][0])
+				continue;
+
+			map.emplace(history[i][0], std::make_tuple(history[i][1], descriptor));
+		}
+
+		for(size_t i(0); i < pos; ++i)
+		{
+			if(!history[i][0])
+				continue;
+
+			map.emplace(history[i][0], std::make_tuple(history[i][1], descriptor));
+		}
+	}
+
+	uint64_t last(0);
+	for(const auto &[epoch, tuple] : map)
+	{
+		const auto &[cyc, desc]
+		{
+			tuple
+		};
+
+		const char ch
+		{
+			epoch == last + 1? '|': 'T'
+		};
+
+		out
+		<< " " << ch
+		<< std::right
+		<< " " << std::setw(12) << epoch
+		<< " " << std::setw(12) << cyc
+		<< " " << std::left << std::setw(36) << desc->name;
+
+		out
+		<< std::endl;
+
+		last = epoch;
+	}
+
+	return true;
+}
+
+bool
+console_cmd__ios__history(opt &out, const string_view &line)
+{
+	for(const auto *const &descriptor : ios::descriptor::list)
+	{
+		assert(descriptor);
+		const auto &d(*descriptor);
+
+		const auto &history(d.history);
+		const auto &pos(d.history_pos);
+
+		out
+		<< std::left << std::setw(3) << d.id
+		<< " " << std::left << std::setw(48) << d.name
+		<< std::endl;
+
+		size_t k(0);
+		for(size_t i(pos); i < 256; ++i)
+		{
+			if(!history[i][0])
+				continue;
+
+			out
+			<< "[" << std::right << std::setw(9) << history[i][0]
+			<< " |" << std::right << std::setw(9) << history[i][1]
+			<< "] ";
+
+			if(++k % 12 == 0)
+				out << std::endl;
+		}
+
+		for(size_t i(0); i < pos; ++i)
+		{
+			if(!history[i][0])
+				continue;
+
+			out
+			<< "[" << std::right << std::setw(9) << history[i][0]
+			<< " |" << std::right << std::setw(9) << history[i][1]
+			<< "] ";
+
+			if(++k % 12 == 0)
+				out << std::endl;
+		}
+
+		out << std::endl;
+	}
+
+	return true;
+}
+
 bool
 console_cmd__ios__depth(opt &out, const string_view &line)
 {