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Diffstat (limited to 'tvix/eval/src/observer.rs')
| -rw-r--r-- | tvix/eval/src/observer.rs | 318 |
1 files changed, 318 insertions, 0 deletions
diff --git a/tvix/eval/src/observer.rs b/tvix/eval/src/observer.rs new file mode 100644 index 0000000000..f5de399315 --- /dev/null +++ b/tvix/eval/src/observer.rs @@ -0,0 +1,318 @@ +//! Implements traits for things that wish to observe internal state +//! changes of tvix-eval. +//! +//! This can be used to gain insights from compilation, to trace the +//! runtime, and so on. +//! +//! All methods are optional, that is, observers can implement only +/// what they are interested in observing. +use std::io::Write; +use std::rc::Rc; +use std::time::Instant; +use tabwriter::TabWriter; + +use crate::chunk::Chunk; +use crate::generators::VMRequest; +use crate::opcode::{CodeIdx, OpCode}; +use crate::value::Lambda; +use crate::SourceCode; +use crate::Value; + +/// Implemented by types that wish to observe internal happenings of +/// the Tvix compiler. +pub trait CompilerObserver { + /// Called when the compiler finishes compilation of the top-level + /// of an expression (usually the root Nix expression of a file). + fn observe_compiled_toplevel(&mut self, _: &Rc<Lambda>) {} + + /// Called when the compiler finishes compilation of a + /// user-defined function. + /// + /// Note that in Nix there are only single argument functions, so + /// in an expression like `a: b: c: ...` this method will be + /// called three times. + fn observe_compiled_lambda(&mut self, _: &Rc<Lambda>) {} + + /// Called when the compiler finishes compilation of a thunk. + fn observe_compiled_thunk(&mut self, _: &Rc<Lambda>) {} +} + +/// Implemented by types that wish to observe internal happenings of +/// the Tvix virtual machine at runtime. +pub trait RuntimeObserver { + /// Called when the runtime enters a new call frame. + fn observe_enter_call_frame(&mut self, _arg_count: usize, _: &Rc<Lambda>, _call_depth: usize) {} + + /// Called when the runtime exits a call frame. + fn observe_exit_call_frame(&mut self, _frame_at: usize, _stack: &[Value]) {} + + /// Called when the runtime suspends a call frame. + fn observe_suspend_call_frame(&mut self, _frame_at: usize, _stack: &[Value]) {} + + /// Called when the runtime enters a generator frame. + fn observe_enter_generator(&mut self, _frame_at: usize, _name: &str, _stack: &[Value]) {} + + /// Called when the runtime exits a generator frame. + fn observe_exit_generator(&mut self, _frame_at: usize, _name: &str, _stack: &[Value]) {} + + /// Called when the runtime suspends a generator frame. + fn observe_suspend_generator(&mut self, _frame_at: usize, _name: &str, _stack: &[Value]) {} + + /// Called when a generator requests an action from the VM. + fn observe_generator_request(&mut self, _name: &str, _msg: &VMRequest) {} + + /// Called when the runtime replaces the current call frame for a + /// tail call. + fn observe_tail_call(&mut self, _frame_at: usize, _: &Rc<Lambda>) {} + + /// Called when the runtime enters a builtin. + fn observe_enter_builtin(&mut self, _name: &'static str) {} + + /// Called when the runtime exits a builtin. + fn observe_exit_builtin(&mut self, _name: &'static str, _stack: &[Value]) {} + + /// Called when the runtime *begins* executing an instruction. The + /// provided stack is the state at the beginning of the operation. + fn observe_execute_op(&mut self, _ip: CodeIdx, _: &OpCode, _: &[Value]) {} +} + +#[derive(Default)] +pub struct NoOpObserver {} + +impl CompilerObserver for NoOpObserver {} +impl RuntimeObserver for NoOpObserver {} + +/// An observer that prints disassembled chunk information to its +/// internal writer whenwever the compiler emits a toplevel function, +/// closure or thunk. +pub struct DisassemblingObserver<W: Write> { + source: SourceCode, + writer: TabWriter<W>, +} + +impl<W: Write> DisassemblingObserver<W> { + pub fn new(source: SourceCode, writer: W) -> Self { + Self { + source, + writer: TabWriter::new(writer), + } + } + + fn lambda_header(&mut self, kind: &str, lambda: &Rc<Lambda>) { + let _ = writeln!( + &mut self.writer, + "=== compiled {} @ {:p} ({} ops) ===", + kind, + *lambda, + lambda.chunk.code.len() + ); + } + + fn disassemble_chunk(&mut self, chunk: &Chunk) { + // calculate width of the widest address in the chunk + let width = format!("{:#x}", chunk.code.len() - 1).len(); + + for (idx, _) in chunk.code.iter().enumerate() { + let _ = chunk.disassemble_op(&mut self.writer, &self.source, width, CodeIdx(idx)); + } + } +} + +impl<W: Write> CompilerObserver for DisassemblingObserver<W> { + fn observe_compiled_toplevel(&mut self, lambda: &Rc<Lambda>) { + self.lambda_header("toplevel", lambda); + self.disassemble_chunk(&lambda.chunk); + let _ = self.writer.flush(); + } + + fn observe_compiled_lambda(&mut self, lambda: &Rc<Lambda>) { + self.lambda_header("lambda", lambda); + self.disassemble_chunk(&lambda.chunk); + let _ = self.writer.flush(); + } + + fn observe_compiled_thunk(&mut self, lambda: &Rc<Lambda>) { + self.lambda_header("thunk", lambda); + self.disassemble_chunk(&lambda.chunk); + let _ = self.writer.flush(); + } +} + +/// An observer that collects a textual representation of an entire +/// runtime execution. +pub struct TracingObserver<W: Write> { + // If timing is enabled, contains the timestamp of the last-emitted trace event + last_event: Option<Instant>, + writer: TabWriter<W>, +} + +impl<W: Write> TracingObserver<W> { + pub fn new(writer: W) -> Self { + Self { + last_event: None, + writer: TabWriter::new(writer), + } + } + + /// Write the time of each runtime event, relative to when this method is called + pub fn enable_timing(&mut self) { + self.last_event = Some(Instant::now()); + } + + fn maybe_write_time(&mut self) { + if let Some(last_event) = &mut self.last_event { + let _ = write!(&mut self.writer, "+{}ns\t", last_event.elapsed().as_nanos()); + *last_event = Instant::now(); + } + } + + fn write_value(&mut self, val: &Value) { + let _ = match val { + // Potentially large types which we only want to print + // the type of (and avoid recursing). + Value::List(l) => write!(&mut self.writer, "list[{}] ", l.len()), + Value::Attrs(a) => write!(&mut self.writer, "attrs[{}] ", a.len()), + Value::Thunk(t) if t.is_evaluated() => { + self.write_value(&t.value()); + Ok(()) + } + + // For other value types, defer to the standard value printer. + _ => write!(&mut self.writer, "{} ", val), + }; + } + + fn write_stack(&mut self, stack: &[Value]) { + let _ = write!(&mut self.writer, "[ "); + + // Print out a maximum of 6 values from the top of the stack, + // before abbreviating it to `...`. + for (i, val) in stack.iter().rev().enumerate() { + if i == 6 { + let _ = write!(&mut self.writer, "..."); + break; + } + + self.write_value(val); + } + + let _ = writeln!(&mut self.writer, "]"); + } +} + +impl<W: Write> RuntimeObserver for TracingObserver<W> { + fn observe_enter_call_frame( + &mut self, + arg_count: usize, + lambda: &Rc<Lambda>, + call_depth: usize, + ) { + self.maybe_write_time(); + + let _ = write!(&mut self.writer, "=== entering "); + + let _ = if arg_count == 0 { + write!(&mut self.writer, "thunk ") + } else { + write!(&mut self.writer, "closure ") + }; + + if let Some(name) = &lambda.name { + let _ = write!(&mut self.writer, "'{}' ", name); + } + + let _ = writeln!( + &mut self.writer, + "in frame[{}] @ {:p} ===", + call_depth, *lambda + ); + } + + /// Called when the runtime exits a call frame. + fn observe_exit_call_frame(&mut self, frame_at: usize, stack: &[Value]) { + self.maybe_write_time(); + let _ = write!(&mut self.writer, "=== exiting frame {} ===\t ", frame_at); + self.write_stack(stack); + } + + fn observe_suspend_call_frame(&mut self, frame_at: usize, stack: &[Value]) { + self.maybe_write_time(); + let _ = write!(&mut self.writer, "=== suspending frame {} ===\t", frame_at); + + self.write_stack(stack); + } + + fn observe_enter_generator(&mut self, frame_at: usize, name: &str, stack: &[Value]) { + self.maybe_write_time(); + let _ = write!( + &mut self.writer, + "=== entering generator frame '{}' [{}] ===\t", + name, frame_at, + ); + + self.write_stack(stack); + } + + fn observe_exit_generator(&mut self, frame_at: usize, name: &str, stack: &[Value]) { + self.maybe_write_time(); + let _ = write!( + &mut self.writer, + "=== exiting generator '{}' [{}] ===\t", + name, frame_at + ); + + self.write_stack(stack); + } + + fn observe_suspend_generator(&mut self, frame_at: usize, name: &str, stack: &[Value]) { + self.maybe_write_time(); + let _ = write!( + &mut self.writer, + "=== suspending generator '{}' [{}] ===\t", + name, frame_at + ); + + self.write_stack(stack); + } + + fn observe_generator_request(&mut self, name: &str, msg: &VMRequest) { + self.maybe_write_time(); + let _ = writeln!( + &mut self.writer, + "=== generator '{}' requested {} ===", + name, msg + ); + } + + fn observe_enter_builtin(&mut self, name: &'static str) { + self.maybe_write_time(); + let _ = writeln!(&mut self.writer, "=== entering builtin {} ===", name); + } + + fn observe_exit_builtin(&mut self, name: &'static str, stack: &[Value]) { + self.maybe_write_time(); + let _ = write!(&mut self.writer, "=== exiting builtin {} ===\t", name); + self.write_stack(stack); + } + + fn observe_tail_call(&mut self, frame_at: usize, lambda: &Rc<Lambda>) { + self.maybe_write_time(); + let _ = writeln!( + &mut self.writer, + "=== tail-calling {:p} in frame[{}] ===", + *lambda, frame_at + ); + } + + fn observe_execute_op(&mut self, ip: CodeIdx, op: &OpCode, stack: &[Value]) { + self.maybe_write_time(); + let _ = write!(&mut self.writer, "{:04} {:?}\t", ip.0, op); + self.write_stack(stack); + } +} + +impl<W: Write> Drop for TracingObserver<W> { + fn drop(&mut self) { + let _ = self.writer.flush(); + } +} |