YJIT: implement two-step call threshold (#8839)

* YJIT: implement two-step call threshold

Automatically switch call threshold to a larger value for
larger, production-sized apps, while still allowing smaller apps
and command-line programs to start with a lower threshold.

* Update yjit/src/options.rs

Co-authored-by: Alan Wu <XrXr@users.noreply.github.com>

* Make the new variables constants

* Check that a custom call threshold was not specified

---------

Co-authored-by: Alan Wu <XrXr@users.noreply.github.com>

Author: maximecb

yjit/src/options.rs

@@ -2,17 +2,26 @@ use std::{ffi::{CStr, CString}, ptr::null};
 use crate::backend::current::TEMP_REGS;
 use std::os::raw::{c_char, c_int, c_uint};
 
+// Call threshold for small deployments and command-line apps
+pub static SMALL_CALL_THRESHOLD: u64 = 30;
+
+// Call threshold for larger deployments and production-sized applications
+pub static LARGE_CALL_THRESHOLD: u64 = 120;
+
+// Number of live ISEQs after which we consider an app to be large
+pub static LARGE_ISEQ_COUNT: u64 = 40_000;
+
 // This option is exposed to the C side a a global variable for performance, see vm.c
 // Number of method calls after which to start generating code
 // Threshold==1 means compile on first execution
 #[no_mangle]
-static mut rb_yjit_call_threshold: u64 = 30;
+pub static mut rb_yjit_call_threshold: u64 = SMALL_CALL_THRESHOLD;
 
 // This option is exposed to the C side a a global variable for performance, see vm.c
 // Number of execution requests after which a method is no longer
 // considered hot. Raising this results in more generated code.
 #[no_mangle]
-static mut rb_yjit_cold_threshold: u64 = 200_000;
+pub static mut rb_yjit_cold_threshold: u64 = 200_000;
 
 // Command-line options
 #[derive(Clone, PartialEq, Eq, Debug)]
@@ -92,7 +101,7 @@ static YJIT_OPTIONS: [(&str, &str); 8] = [
     ("--yjit-trace-exits",              "Record Ruby source location when exiting from generated code"),
     ("--yjit-trace-exits-sample-rate",  "Trace exit locations only every Nth occurrence"),
     ("--yjit-exec-mem-size=num",        "Size of executable memory block in MiB (default: 128)"),
-    ("--yjit-call-threshold=num",       "Number of calls to trigger JIT (default: 30)"),
+    ("--yjit-call-threshold=num",       "Number of calls to trigger JIT"),
     ("--yjit-cold-threshold=num",       "Global call after which ISEQs not compiled (default: 200K)"),
     ("--yjit-max-versions=num",         "Maximum number of versions per basic block (default: 4)"),
     ("--yjit-perf",                     "Enable frame pointers and perf profiling"),

yjit/src/yjit.rs

@@ -134,6 +134,14 @@ pub extern "C" fn rb_yjit_iseq_gen_entry_point(iseq: IseqPtr, ec: EcPtr, jit_exc
         return std::ptr::null();
     }
 
+    // If a custom call threshold was not specified on the command-line and
+    // this is a large application (has very many ISEQs), switch to
+    // using the call threshold for large applications after this entry point
+    use crate::stats::rb_yjit_live_iseq_count;
+    if unsafe { rb_yjit_call_threshold } == SMALL_CALL_THRESHOLD && unsafe { rb_yjit_live_iseq_count } > LARGE_ISEQ_COUNT {
+        unsafe { rb_yjit_call_threshold = LARGE_CALL_THRESHOLD; };
+    }
+
     let maybe_code_ptr = with_compile_time(|| { gen_entry_point(iseq, ec, jit_exception) });
 
     match maybe_code_ptr {