Enum fidl_fuchsia_memorypressure::WatcherRequest

pub enum WatcherRequest {
    OnLevelChanged {
        level: Level,
        responder: WatcherOnLevelChangedResponder,
    },
}

Watcher protocol To be implemented by clients who wish to be notified on memory pressure level changes.

Variants

OnLevelChanged

Sent to the registered client when the memory pressure level changes. level: indicates the current memory pressure level.

Will also be invoked on initial connection via RegisterWatcher, so that a newly registered client can discover the current memory pressure level.

The watcher must immediately reply with a message to acknowledge that it has received the level change notification, and has initiated required actions as a result. It may then continue to reclaim memory asynchronously after sending the acknowledgement.

Some helpful guidelines for clients:

1. The watcher will be notified of new pressure level changes only after a reply corresponding to the previous message has been received by the provider. If multiple level transitions occur during that time, the watcher will be notified of the latest pressure level.

2. The level changes are edge-triggered, and clients are expected to maintain local state to track the current pressure level, if required. For example, a job might be notified of a CRITICAL level and drop all its caches as a result. Some time after this, it might want to trigger an activity that causes a fair amount of memory to be allocated. At this point, the job is expected to remember that the last pressure level it saw was CRITICAL, and refrain from triggering the memory-intensive activity.

3. As a performance optimization, the provider may decide to skip sending messages for some pressure level changes. For example, when oscillating across the NORMAL / WARNING boundary, it might not be worth notifying clients of every single transition. The provider might rate-limit messages in this case. On a similar note, the provider may decide to send repeated messages at the same pressure level, particularly CRITICAL, to indicate that further action needs to be taken.

Fields

level: Level

responder: WatcherOnLevelChangedResponder

Implementations

impl WatcherRequest

pub fn into_on_level_changed( self ) -> Option<(Level, WatcherOnLevelChangedResponder)>

pub fn method_name(&self) -> &'static str

Name of the method defined in FIDL

Trait Implementations

impl Debug for WatcherRequest

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.