Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/stdx/src/thread/intent.rs')
| -rw-r--r-- | crates/stdx/src/thread/intent.rs | 287 |
1 files changed, 287 insertions, 0 deletions
diff --git a/crates/stdx/src/thread/intent.rs b/crates/stdx/src/thread/intent.rs new file mode 100644 index 0000000000..7b65db30cc --- /dev/null +++ b/crates/stdx/src/thread/intent.rs @@ -0,0 +1,287 @@ +//! An opaque façade around platform-specific QoS APIs. + +#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)] +// Please maintain order from least to most priority for the derived `Ord` impl. +pub enum ThreadIntent { + /// Any thread which does work that isn’t in the critical path of the user typing + /// (e.g. processing Go To Definition). + Worker, + + /// Any thread which does work caused by the user typing + /// (e.g. processing syntax highlighting). + LatencySensitive, +} + +impl ThreadIntent { + // These APIs must remain private; + // we only want consumers to set thread intent + // either during thread creation or using our pool impl. + + pub(super) fn apply_to_current_thread(self) { + let class = thread_intent_to_qos_class(self); + set_current_thread_qos_class(class); + } + + pub(super) fn assert_is_used_on_current_thread(self) { + if IS_QOS_AVAILABLE { + let class = thread_intent_to_qos_class(self); + assert_eq!(get_current_thread_qos_class(), Some(class)); + } + } +} + +use imp::QoSClass; + +const IS_QOS_AVAILABLE: bool = imp::IS_QOS_AVAILABLE; + +fn set_current_thread_qos_class(class: QoSClass) { + imp::set_current_thread_qos_class(class) +} + +fn get_current_thread_qos_class() -> Option<QoSClass> { + imp::get_current_thread_qos_class() +} + +fn thread_intent_to_qos_class(intent: ThreadIntent) -> QoSClass { + imp::thread_intent_to_qos_class(intent) +} + +// All Apple platforms use XNU as their kernel +// and thus have the concept of QoS. +#[cfg(target_vendor = "apple")] +mod imp { + use super::ThreadIntent; + + #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)] + // Please maintain order from least to most priority for the derived `Ord` impl. + pub(super) enum QoSClass { + // Documentation adapted from https://github.com/apple-oss-distributions/libpthread/blob/67e155c94093be9a204b69637d198eceff2c7c46/include/sys/qos.h#L55 + // + /// TLDR: invisible maintenance tasks + /// + /// Contract: + /// + /// * **You do not care about how long it takes for work to finish.** + /// * **You do not care about work being deferred temporarily.** + /// (e.g. if the device’s battery is in a critical state) + /// + /// Examples: + /// + /// * in a video editor: + /// creating periodic backups of project files + /// * in a browser: + /// cleaning up cached sites which have not been accessed in a long time + /// * in a collaborative word processor: + /// creating a searchable index of all documents + /// + /// Use this QoS class for background tasks + /// which the user did not initiate themselves + /// and which are invisible to the user. + /// It is expected that this work will take significant time to complete: + /// minutes or even hours. + /// + /// This QoS class provides the most energy and thermally-efficient execution possible. + /// All other work is prioritized over background tasks. + Background, + + /// TLDR: tasks that don’t block using your app + /// + /// Contract: + /// + /// * **Your app remains useful even as the task is executing.** + /// + /// Examples: + /// + /// * in a video editor: + /// exporting a video to disk – + /// the user can still work on the timeline + /// * in a browser: + /// automatically extracting a downloaded zip file – + /// the user can still switch tabs + /// * in a collaborative word processor: + /// downloading images embedded in a document – + /// the user can still make edits + /// + /// Use this QoS class for tasks which + /// may or may not be initiated by the user, + /// but whose result is visible. + /// It is expected that this work will take a few seconds to a few minutes. + /// Typically your app will include a progress bar + /// for tasks using this class. + /// + /// This QoS class provides a balance between + /// performance, responsiveness and efficiency. + Utility, + + /// TLDR: tasks that block using your app + /// + /// Contract: + /// + /// * **You need this work to complete + /// before the user can keep interacting with your app.** + /// * **Your work will not take more than a few seconds to complete.** + /// + /// Examples: + /// + /// * in a video editor: + /// opening a saved project + /// * in a browser: + /// loading a list of the user’s bookmarks and top sites + /// when a new tab is created + /// * in a collaborative word processor: + /// running a search on the document’s content + /// + /// Use this QoS class for tasks which were initiated by the user + /// and block the usage of your app while they are in progress. + /// It is expected that this work will take a few seconds or less to complete; + /// not long enough to cause the user to switch to something else. + /// Your app will likely indicate progress on these tasks + /// through the display of placeholder content or modals. + /// + /// This QoS class is not energy-efficient. + /// Rather, it provides responsiveness + /// by prioritizing work above other tasks on the system + /// except for critical user-interactive work. + UserInitiated, + + /// TLDR: render loops and nothing else + /// + /// Contract: + /// + /// * **You absolutely need this work to complete immediately + /// or your app will appear to freeze.** + /// * **Your work will always complete virtually instantaneously.** + /// + /// Examples: + /// + /// * the main thread in a GUI application + /// * the update & render loop in a game + /// * a secondary thread which progresses an animation + /// + /// Use this QoS class for any work which, if delayed, + /// will make your user interface unresponsive. + /// It is expected that this work will be virtually instantaneous. + /// + /// This QoS class is not energy-efficient. + /// Specifying this class is a request to run with + /// nearly all available system CPU and I/O bandwidth even under contention. + UserInteractive, + } + + pub(super) const IS_QOS_AVAILABLE: bool = true; + + pub(super) fn set_current_thread_qos_class(class: QoSClass) { + let c = match class { + QoSClass::UserInteractive => libc::qos_class_t::QOS_CLASS_USER_INTERACTIVE, + QoSClass::UserInitiated => libc::qos_class_t::QOS_CLASS_USER_INITIATED, + QoSClass::Utility => libc::qos_class_t::QOS_CLASS_UTILITY, + QoSClass::Background => libc::qos_class_t::QOS_CLASS_BACKGROUND, + }; + + let code = unsafe { libc::pthread_set_qos_class_self_np(c, 0) }; + + if code == 0 { + return; + } + + let errno = unsafe { *libc::__error() }; + + match errno { + libc::EPERM => { + // This thread has been excluded from the QoS system + // due to a previous call to a function such as `pthread_setschedparam` + // which is incompatible with QoS. + // + // Panic instead of returning an error + // to maintain the invariant that we only use QoS APIs. + panic!("tried to set QoS of thread which has opted out of QoS (os error {errno})") + } + + libc::EINVAL => { + // This is returned if we pass something other than a qos_class_t + // to `pthread_set_qos_class_self_np`. + // + // This is impossible, so again panic. + unreachable!( + "invalid qos_class_t value was passed to pthread_set_qos_class_self_np" + ) + } + + _ => { + // `pthread_set_qos_class_self_np`’s documentation + // does not mention any other errors. + unreachable!("`pthread_set_qos_class_self_np` returned unexpected error {errno}") + } + } + } + + pub(super) fn get_current_thread_qos_class() -> Option<QoSClass> { + let current_thread = unsafe { libc::pthread_self() }; + let mut qos_class_raw = libc::qos_class_t::QOS_CLASS_UNSPECIFIED; + let code = unsafe { + libc::pthread_get_qos_class_np(current_thread, &mut qos_class_raw, std::ptr::null_mut()) + }; + + if code != 0 { + // `pthread_get_qos_class_np`’s documentation states that + // an error value is placed into errno if the return code is not zero. + // However, it never states what errors are possible. + // Inspecting the source[0] shows that, as of this writing, it always returns zero. + // + // Whatever errors the function could report in future are likely to be + // ones which we cannot handle anyway + // + // 0: https://github.com/apple-oss-distributions/libpthread/blob/67e155c94093be9a204b69637d198eceff2c7c46/src/qos.c#L171-L177 + let errno = unsafe { *libc::__error() }; + unreachable!("`pthread_get_qos_class_np` failed unexpectedly (os error {errno})"); + } + + match qos_class_raw { + libc::qos_class_t::QOS_CLASS_USER_INTERACTIVE => Some(QoSClass::UserInteractive), + libc::qos_class_t::QOS_CLASS_USER_INITIATED => Some(QoSClass::UserInitiated), + libc::qos_class_t::QOS_CLASS_DEFAULT => None, // QoS has never been set + libc::qos_class_t::QOS_CLASS_UTILITY => Some(QoSClass::Utility), + libc::qos_class_t::QOS_CLASS_BACKGROUND => Some(QoSClass::Background), + + libc::qos_class_t::QOS_CLASS_UNSPECIFIED => { + // Using manual scheduling APIs causes threads to “opt out” of QoS. + // At this point they become incompatible with QoS, + // and as such have the “unspecified” QoS class. + // + // Panic instead of returning an error + // to maintain the invariant that we only use QoS APIs. + panic!("tried to get QoS of thread which has opted out of QoS") + } + } + } + + pub(super) fn thread_intent_to_qos_class(intent: ThreadIntent) -> QoSClass { + match intent { + ThreadIntent::Worker => QoSClass::Utility, + ThreadIntent::LatencySensitive => QoSClass::UserInitiated, + } + } +} + +// FIXME: Windows has QoS APIs, we should use them! +#[cfg(not(target_vendor = "apple"))] +mod imp { + use super::ThreadIntent; + + #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)] + pub(super) enum QoSClass { + Default, + } + + pub(super) const IS_QOS_AVAILABLE: bool = false; + + pub(super) fn set_current_thread_qos_class(_: QoSClass) {} + + pub(super) fn get_current_thread_qos_class() -> Option<QoSClass> { + None + } + + pub(super) fn thread_intent_to_qos_class(_: ThreadIntent) -> QoSClass { + QoSClass::Default + } +} |