From 582652e70999b96470dc76a5059c02c1e8d7af74 Mon Sep 17 00:00:00 2001 From: Anand Bonde Date: Fri, 7 Jun 2024 22:28:40 +0000 Subject: [PATCH] [runtime] Enhancement: Adaptable timer res --- src/rust/runtime/mod.rs | 81 +++++++++++++++++++++++++++++++++-------- 1 file changed, 66 insertions(+), 15 deletions(-) diff --git a/src/rust/runtime/mod.rs b/src/rust/runtime/mod.rs index 38fa874e5..0aa402d74 100644 --- a/src/rust/runtime/mod.rs +++ b/src/rust/runtime/mod.rs @@ -27,6 +27,7 @@ pub use queue::{ QType, }; pub use scheduler::TaskId; +use x86::time::rdtscp; #[cfg(feature = "libdpdk")] pub use dpdk_rs as libdpdk; @@ -82,16 +83,21 @@ use ::std::{ SystemTime, }, }; -use std::pin::Pin; +use std::{ + cmp::{ + max, + min, + }, + pin::Pin, +}; //====================================================================================================================== // Constants //====================================================================================================================== -// TODO: Make this more accurate using rdtsc. -// FIXME: https://github.com/microsoft/demikernel/issues/1226 -const TIMER_RESOLUTION: usize = 64; -const TIMER_FINER_RESOLUTION: usize = 2; +const MIN_TIMER_RESOLUTION: usize = 64; +const MAX_TIMER_RESOLUTION: usize = 64_000; +const FINE_TIMER_RESOLUTION: usize = 2; //====================================================================================================================== // Structures @@ -109,6 +115,12 @@ pub struct DemiRuntime { network_table: NetworkQueueTable, /// Number of iterations that we have polled since advancing the clock. ts_iters: usize, + /// Last tsc counter value. + last_tsc: u64, + /// List time instant. + last_time: Instant, + /// Timer resolution. + timer_resolution: usize, /// Tasks that have been completed and removed from the completed_tasks: HashMap, } @@ -146,6 +158,12 @@ impl SharedDemiRuntime { ephemeral_ports: EphemeralPorts::default(), network_table: NetworkQueueTable::default(), ts_iters: 0, + last_tsc: unsafe { + let (rdtscp, _) = rdtscp(); + rdtscp + }, + last_time: Instant::now(), + timer_resolution: MIN_TIMER_RESOLUTION, completed_tasks: HashMap::::new(), })) } @@ -212,11 +230,12 @@ impl SharedDemiRuntime { return Err(Fail::new(libc::EINVAL, &cause)); } - // 2. None of the tasks have already completed, so start a timer and move the clock. - self.advance_clock_to_now(); + // None of the tasks have already completed. loop { - if let Some(boxed_task) = self.scheduler.get_next_completed_task(TIMER_RESOLUTION) { + self.advance_clock_to_now(); + let max_iterations = self.timer_resolution; + if let Some(boxed_task) = self.scheduler.get_next_completed_task(max_iterations) { // Perform bookkeeping for the completed and removed task. trace!("Removing coroutine: {:?}", boxed_task.get_name()); let completed_qt: QToken = boxed_task.get_id().into(); @@ -240,9 +259,6 @@ impl SharedDemiRuntime { return Err(Fail::new(libc::ETIMEDOUT, "wait timed out")); } } - - // Advance the clock and continue running tasks. - self.advance_clock_to_now(); } } @@ -359,8 +375,8 @@ impl SharedDemiRuntime { /// the clock. fn run_next(&mut self, timeout: Duration) -> Option<(QToken, QDesc, OperationResult)> { let iterations: usize = match timeout { - timeout if timeout.as_secs() > 0 => TIMER_RESOLUTION, - _ => TIMER_FINER_RESOLUTION, + timeout if timeout.as_secs() > 0 => self.timer_resolution, + _ => FINE_TIMER_RESOLUTION, }; if let Some(boxed_task) = self.scheduler.get_next_completed_task(iterations) { // Perform bookkeeping for the completed and removed task. @@ -478,7 +494,8 @@ impl SharedDemiRuntime { /// Moves time forward deterministically. pub fn advance_clock(&mut self, now: Instant) { - timer::global_advance_clock(now) + timer::global_advance_clock(now); + self.adjust_time_resolution(now); } /// Moves time forward to the current real time. @@ -486,7 +503,7 @@ impl SharedDemiRuntime { if self.ts_iters == 0 { self.advance_clock(Instant::now()); } - self.ts_iters = (self.ts_iters + 1) % TIMER_RESOLUTION; + self.ts_iters = (self.ts_iters + 1) % self.timer_resolution; } /// Gets the current time according to our internal timer. @@ -535,6 +552,34 @@ impl SharedDemiRuntime { trace!("Check address in use: {:?}", local); self.network_table.addr_in_use(local) } + + fn adjust_time_resolution(&mut self, now: Instant) { + let curr_tsc: u64 = unsafe { + let (tsc, _): (u64, u32) = rdtscp(); + tsc + }; + let cycles: usize = (curr_tsc - self.last_tsc) as usize; + + let time_in_seconds = (now - self.last_time).as_secs(); + if time_in_seconds == 0 { + return; + } + + let cycles_per_second: usize = cycles / time_in_seconds as usize; + if cycles_per_second == 0 { + return; + } + + let cycles_per_quanta: usize = cycles_per_second / MIN_TIMER_RESOLUTION; + if cycles_per_quanta == 0 { + return; + } + + self.timer_resolution = max(MIN_TIMER_RESOLUTION, min(MAX_TIMER_RESOLUTION, cycles_per_quanta)); + trace!("Adjusted timer resolution to: {:?}", self.timer_resolution); + self.last_tsc = curr_tsc; + self.last_time = now; + } } impl SharedObject { @@ -597,6 +642,12 @@ impl Default for SharedDemiRuntime { ephemeral_ports: EphemeralPorts::default(), network_table: NetworkQueueTable::default(), ts_iters: 0, + last_tsc: unsafe { + let (tsc, _) = rdtscp(); + tsc + }, + last_time: Instant::now(), + timer_resolution: MIN_TIMER_RESOLUTION, completed_tasks: HashMap::::new(), })) }