From 854baee2c936006d7f38ebb27ee577c00afc6249 Mon Sep 17 00:00:00 2001 From: Adam Hess Date: Thu, 13 Apr 2023 07:07:07 -0700 Subject: YJIT: Add a sampling option to exit tracing (#7693) Add a sampling option to trace exits Running YJIT with trace exits enabled can make very large metrics files. This allows us to configure a sample rate to make tracing exits possible on larger tests. This also updates the documented YJIT options. Co-authored-by: Alan Wu Co-authored-by: John Hawthorn Co-authored-by: Maxime Chevalier-Boisvert --- yjit/src/options.rs | 20 +++++++++++++++++++- yjit/src/stats.rs | 21 +++++++++++++++++++-- 2 files changed, 38 insertions(+), 3 deletions(-) (limited to 'yjit') diff --git a/yjit/src/options.rs b/yjit/src/options.rs index 03acc7bbe0..78a507ce11 100644 --- a/yjit/src/options.rs +++ b/yjit/src/options.rs @@ -32,6 +32,9 @@ pub struct Options { // Trace locations of exits pub gen_trace_exits: bool, + // how often to sample exit trace data + pub trace_exits_sample_rate: usize, + // Whether to start YJIT in paused state (initialize YJIT but don't // compile anything) pub pause: bool, @@ -59,6 +62,7 @@ pub static mut OPTIONS: Options = Options { num_temp_regs: 5, gen_stats: false, gen_trace_exits: false, + trace_exits_sample_rate: 0, pause: false, dump_insns: false, dump_disasm: None, @@ -173,7 +177,8 @@ pub fn parse_option(str_ptr: *const std::os::raw::c_char) -> Option<()> { ("greedy-versioning", "") => unsafe { OPTIONS.greedy_versioning = true }, ("no-type-prop", "") => unsafe { OPTIONS.no_type_prop = true }, ("stats", "") => unsafe { OPTIONS.gen_stats = true }, - ("trace-exits", "") => unsafe { OPTIONS.gen_trace_exits = true; OPTIONS.gen_stats = true }, + ("trace-exits", "") => unsafe { OPTIONS.gen_trace_exits = true; OPTIONS.gen_stats = true; OPTIONS.trace_exits_sample_rate = 0 }, + ("trace-exits-sample-rate", sample_rate) => unsafe { OPTIONS.gen_trace_exits = true; OPTIONS.gen_stats = true; OPTIONS.trace_exits_sample_rate = sample_rate.parse().unwrap(); }, ("dump-insns", "") => unsafe { OPTIONS.dump_insns = true }, ("verify-ctx", "") => unsafe { OPTIONS.verify_ctx = true }, @@ -183,6 +188,19 @@ pub fn parse_option(str_ptr: *const std::os::raw::c_char) -> Option<()> { } } + // before we continue, check that sample_rate is either 0 or a prime number + let trace_sample_rate = unsafe { OPTIONS.trace_exits_sample_rate }; + if trace_sample_rate > 1 { + let mut i = 2; + while i*i <= trace_sample_rate { + if trace_sample_rate % i == 0 { + println!("Warning: using a non-prime number as your sampling rate can result in less accurate sampling data"); + return Some(()); + } + i += 1; + } + } + // dbg!(unsafe {OPTIONS}); // Option successfully parsed diff --git a/yjit/src/stats.rs b/yjit/src/stats.rs index f937c6e625..42b7de7a59 100644 --- a/yjit/src/stats.rs +++ b/yjit/src/stats.rs @@ -26,7 +26,9 @@ pub struct YjitExitLocations { raw_samples: Vec, /// Vec to hold line_samples which represent line numbers of /// the iseq caller. - line_samples: Vec + line_samples: Vec, + /// Number of samples skipped when sampling + skipped_samples: usize } /// Private singleton instance of yjit exit locations @@ -47,7 +49,8 @@ impl YjitExitLocations { let yjit_exit_locations = YjitExitLocations { raw_samples: Vec::new(), - line_samples: Vec::new() + line_samples: Vec::new(), + skipped_samples: 0 }; // Initialize the yjit exit locations instance @@ -71,6 +74,11 @@ impl YjitExitLocations { &mut YjitExitLocations::get_instance().line_samples } + /// Get the number of samples skipped + pub fn get_skipped_samples() -> &'static mut usize { + &mut YjitExitLocations::get_instance().skipped_samples + } + /// Mark the data stored in YjitExitLocations::get_raw_samples that needs to be used by /// rb_yjit_add_frame. YjitExitLocations::get_raw_samples are an array of /// VALUE pointers, exit instruction, and number of times we've seen this stack row @@ -573,6 +581,15 @@ pub extern "C" fn rb_yjit_record_exit_stack(exit_pc: *const VALUE) return; } + if get_option!(trace_exits_sample_rate) > 0 { + if get_option!(trace_exits_sample_rate) <= *YjitExitLocations::get_skipped_samples() { + YjitExitLocations::get_instance().skipped_samples = 0; + } else { + YjitExitLocations::get_instance().skipped_samples += 1; + return; + } + } + // rb_vm_insn_addr2opcode won't work in cargo test --all-features // because it's a C function. Without insn call, this function is useless // so wrap the whole thing in a not test check. -- cgit v1.2.1