Struct ConcurrencyRamp 

pub struct ConcurrencyRamp { /* private fields */ }

Drives concurrency upward on a live transfer while it pays to do so.

Implementations

impl ConcurrencyRamp

pub fn starting_at(min_gain_frac: f64, start: usize, max: usize) -> Self

min_gain_frac is the marginal goodput, as a fraction of the single-connection rate, that a new connection must add to be kept. Start the search at start connections rather than at one.

Why the search no longer climbs from one

Climbing costs a measurement window per level, and a window long enough to outlast slow start (see WINDOW_DELTAS) is long enough that the climb dominates a short transfer. Climbing from one is only worth it if the levels above one are likely to be much better — and on the paths measured, they are not.

The asymmetry, not a claimed win, is what justifies starting low. Measured over 20 paired repetitions on four objects, starting at 1 connection is statistically indistinguishable from a fixed baseline while fixed -x 8 cost 1.37–3.04x, and on a path a single stream already saturates -x 8 incurred a 3.6x slowdown where -x 1 was 1.17x. So the downside of starting high is large and measured; the upside is not.

Starting at one is therefore a conservative policy choice, ensuring minimal overhead while admitting more connections only when headroom is proven.

pub fn new(min_gain_frac: f64, max: usize) -> Self

pub fn start(&mut self, now: f64, delta: f64)

Begin the first window. now is the transfer’s clock, delta the measured per-request setup cost.

pub fn observe(&mut self, bytes: u64, now: f64)

Record bytes delivered by the whole transfer.

Aggregate, not per-connection: the question is whether the path is carrying more, and a per-connection view cannot answer it — on a saturated link each connection’s own rate falls as connections are added while the total stays flat, which is exactly the case the ramp must detect.

pub fn settled(&self) -> Option<usize>

The useful count, once the search has settled.

pub fn level(&self) -> usize

Current concurrency.

pub fn poll(&mut self, now: f64, delta: f64) -> Ramp

Close the window if it is due and decide what to do next.

Trait Implementations

impl Clone for ConcurrencyRamp

fn clone(&self) -> ConcurrencyRamp

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ConcurrencyRamp

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

Formats the value using the given formatter.