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Initialize LLVM time trace profiler on each code generation thread

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In https://reviews.llvm.org/D71059 LLVM 11, the time trace profiler was
extended to support multiple threads.

`timeTraceProfilerInitialize` creates a thread local profiler instance.
When a thread finishes `timeTraceProfilerFinishThread` moves a thread
local instance into a global collection of instances. Finally when all
codegen work is complete `timeTraceProfilerWrite` writes data from the
current thread local instance and the instances in global collection
of instances.

Previously, the profiler was intialized on a single thread only. Since
this thread performs no code generation on its own, the resulting
profile was empty.

Update LLVM codegen to initialize & finish time trace profiler on each
code generation thread.
This commit is contained in:
Tomasz Miąsko 2021-11-05 00:00:00 +00:00
parent d22dd65835
commit 5a09e12135
6 changed files with 128 additions and 56 deletions
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102
compiler/rustc_codegen_ssa/src/back/write.rs
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@ -310,6 +310,7 @@ pub struct CodegenContext<B: WriteBackendMethods> {
pub no_landing_pads: bool,
pub save_temps: bool,
pub fewer_names: bool,
pub time_trace: bool,
pub exported_symbols: Option<Arc<ExportedSymbols>>,
pub opts: Arc<config::Options>,
pub crate_types: Vec<CrateType>,
@ -1039,6 +1040,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
no_landing_pads: sess.panic_strategy() == PanicStrategy::Abort,
fewer_names: sess.fewer_names(),
save_temps: sess.opts.cg.save_temps,
time_trace: sess.opts.debugging_opts.llvm_time_trace,
opts: Arc::new(sess.opts.clone()),
prof: sess.prof.clone(),
exported_symbols,
@ -1198,7 +1200,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
// Each LLVM module is automatically sent back to the coordinator for LTO if
// necessary. There's already optimizations in place to avoid sending work
// back to the coordinator if LTO isn't requested.
return thread::spawn(move || {
return B::spawn_thread(cgcx.time_trace, move || {
let mut worker_id_counter = 0;
let mut free_worker_ids = Vec::new();
let mut get_worker_id = |free_worker_ids: &mut Vec<usize>| {
@ -1615,59 +1617,57 @@ fn start_executing_work<B: ExtraBackendMethods>(
pub struct WorkerFatalError;
fn spawn_work<B: ExtraBackendMethods>(cgcx: CodegenContext<B>, work: WorkItem<B>) {
let builder = thread::Builder::new().name(work.short_description());
builder
.spawn(move || {
// Set up a destructor which will fire off a message that we're done as
// we exit.
struct Bomb<B: ExtraBackendMethods> {
coordinator_send: Sender<Box<dyn Any + Send>>,
result: Option<Result<WorkItemResult<B>, FatalError>>,
worker_id: usize,
}
impl<B: ExtraBackendMethods> Drop for Bomb<B> {
fn drop(&mut self) {
let worker_id = self.worker_id;
let msg = match self.result.take() {
Some(Ok(WorkItemResult::Compiled(m))) => {
Message::Done::<B> { result: Ok(m), worker_id }
}
Some(Ok(WorkItemResult::NeedsLink(m))) => {
Message::NeedsLink::<B> { module: m, worker_id }
}
Some(Ok(WorkItemResult::NeedsFatLTO(m))) => {
Message::NeedsFatLTO::<B> { result: m, worker_id }
}
Some(Ok(WorkItemResult::NeedsThinLTO(name, thin_buffer))) => {
Message::NeedsThinLTO::<B> { name, thin_buffer, worker_id }
}
Some(Err(FatalError)) => {
Message::Done::<B> { result: Err(Some(WorkerFatalError)), worker_id }
}
None => Message::Done::<B> { result: Err(None), worker_id },
};
drop(self.coordinator_send.send(Box::new(msg)));
}
B::spawn_named_thread(cgcx.time_trace, work.short_description(), move || {
// Set up a destructor which will fire off a message that we're done as
// we exit.
struct Bomb<B: ExtraBackendMethods> {
coordinator_send: Sender<Box<dyn Any + Send>>,
result: Option<Result<WorkItemResult<B>, FatalError>>,
worker_id: usize,
}
impl<B: ExtraBackendMethods> Drop for Bomb<B> {
fn drop(&mut self) {
let worker_id = self.worker_id;
let msg = match self.result.take() {
Some(Ok(WorkItemResult::Compiled(m))) => {
Message::Done::<B> { result: Ok(m), worker_id }
}
Some(Ok(WorkItemResult::NeedsLink(m))) => {
Message::NeedsLink::<B> { module: m, worker_id }
}
Some(Ok(WorkItemResult::NeedsFatLTO(m))) => {
Message::NeedsFatLTO::<B> { result: m, worker_id }
}
Some(Ok(WorkItemResult::NeedsThinLTO(name, thin_buffer))) => {
Message::NeedsThinLTO::<B> { name, thin_buffer, worker_id }
}
Some(Err(FatalError)) => {
Message::Done::<B> { result: Err(Some(WorkerFatalError)), worker_id }
}
None => Message::Done::<B> { result: Err(None), worker_id },
};
drop(self.coordinator_send.send(Box::new(msg)));
}
}
let mut bomb = Bomb::<B> {
coordinator_send: cgcx.coordinator_send.clone(),
result: None,
worker_id: cgcx.worker,
};
let mut bomb = Bomb::<B> {
coordinator_send: cgcx.coordinator_send.clone(),
result: None,
worker_id: cgcx.worker,
};
// Execute the work itself, and if it finishes successfully then flag
// ourselves as a success as well.
//
// Note that we ignore any `FatalError` coming out of `execute_work_item`,
// as a diagnostic was already sent off to the main thread - just
// surface that there was an error in this worker.
bomb.result = {
let _prof_timer = work.start_profiling(&cgcx);
Some(execute_work_item(&cgcx, work))
};
})
.expect("failed to spawn thread");
// Execute the work itself, and if it finishes successfully then flag
// ourselves as a success as well.
//
// Note that we ignore any `FatalError` coming out of `execute_work_item`,
// as a diagnostic was already sent off to the main thread - just
// surface that there was an error in this worker.
bomb.result = {
let _prof_timer = work.start_profiling(&cgcx);
Some(execute_work_item(&cgcx, work))
};
})
.expect("failed to spawn thread");
}
enum SharedEmitterMessage {