YJIT: Add counter to measure how often we compile "cold" ISEQs (#535)

yjit.h

@@ -27,6 +27,7 @@
 // Expose these as declarations since we are building YJIT.
 bool rb_yjit_enabled_p(void);
 bool rb_yjit_compile_new_iseqs(void);
+unsigned rb_yjit_call_threshold(void);
 bool rb_yjit_threshold_hit(const rb_iseq_t *const iseq, unsigned long total_calls);
 void rb_yjit_invalidate_all_method_lookup_assumptions(void);
 void rb_yjit_cme_invalidate(rb_callable_method_entry_t *cme);
@@ -49,6 +50,7 @@ void rb_yjit_tracing_invalidate_all(void);
 
 static inline bool rb_yjit_enabled_p(void) { return false; }
 static inline bool rb_yjit_compile_new_iseqs(void) { return false; }
+static inline unsigned rb_yjit_call_threshold(void) { return UINT_MAX; }
 static inline bool rb_yjit_threshold_hit(const rb_iseq_t *const iseq, unsigned long total_calls) { return false; }
 static inline void rb_yjit_invalidate_all_method_lookup_assumptions(void) {}
 static inline void rb_yjit_cme_invalidate(rb_callable_method_entry_t *cme) {}

yjit/src/core.rs

@@ -980,6 +980,9 @@ pub struct IseqPayload {
  // Blocks that are invalidated but are not yet deallocated.
  // The code GC will free them later.
  pub dead_blocks: Vec<BlockRef>,
+
+ // Number of calls when we hit the threshold for this ISEQs
+ pub call_count_at_threshold: u64,
 }
 
 impl IseqPayload {

yjit/src/stats.rs

@@ -201,6 +201,7 @@ macro_rules! make_counters {
 pub const DEFAULT_COUNTERS: [Counter; 7] = [
  Counter::code_gc_count,
  Counter::compiled_iseq_entry,
+ Counter::compiled_iseq_entry_cold,
  Counter::compiled_iseq_count,
  Counter::compiled_blockid_count,
  Counter::compiled_block_count,
@@ -441,6 +442,7 @@ make_counters! {
  binding_set,
 
  compiled_iseq_entry,
+ compiled_entry_cold,
  compiled_iseq_count,
  compiled_blockid_count,
  compiled_block_count,

yjit/src/yjit.rs

@@ -6,6 +6,7 @@ use crate::options::*;
 use crate::stats::YjitExitLocations;
 use crate::stats::incr_counter;
 use crate::stats::with_compile_time;
+use crate::stats::incr_counter;
 
 use std::os::raw;
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -53,6 +54,42 @@ pub extern "C" fn rb_yjit_threshold_hit(_iseq: IseqPtr, total_calls: u64) -> boo
  return total_calls == call_threshold;
 }
 
+// Counter to serve as a proxy for execution time, total number of calls
+static mut TOTAL_ENTRY_HITS: u64 = 0;
+
+/// Test whether we are ready to compile an ISEQ or not
+#[no_mangle]
+pub extern "C" fn rb_yjit_threshold_hit(iseq: IseqPtr, total_calls: u64) -> bool {
+ let call_threshold = get_option!(call_threshold) as u64;
+
+ unsafe { TOTAL_ENTRY_HITS += 1; }
+
+ if total_calls >= call_threshold {
+
+ if total_calls == call_threshold {
+ let payload = get_or_create_iseq_payload(iseq);
+ let call_count = unsafe { TOTAL_ENTRY_HITS };
+ payload.call_count_at_threshold = call_count;
+ }
+
+ // Try to estimate the total time taken (total number of calls) to reach 20 calls to this ISEQ
+ // This give us a ratio of how hot/cold this ISEQ is
+ if total_calls == call_threshold + 20 {
+ let payload = get_or_create_iseq_payload(iseq);
+ let call_count = unsafe { TOTAL_ENTRY_HITS };
+ let num_calls = call_count - payload.call_count_at_threshold;
+
+ if num_calls > 50_000 {
+ incr_counter!(compiled_entry_cold);
+ }
+
+ return true;
+ }
+ }
+
+ return false;
+}
+
 /// This function is called from C code
 #[no_mangle]
 pub extern "C" fn rb_yjit_init_rust() {