Found some `if let` statements that don't actually bind any variables.
This can make it somewhat confusing as to whether the pattern is binding
the value or being matched against. Switching to `matches!` and equality
comparisons allow these to be removed.
Co-authored-by: David Koloski <dkoloski@google.com>
This doesn't cause any issues in practice because this is a private API
that is only used in ways that cannot trigger UB. Indexing into `slots`
is not sound until after we've asserted that the page is allocated,
since that aliases the first slot which may not be allocated. This PR
also switches to using `as_ptr` to obtain the base pointer for clarity.
Co-authored-by: David Koloski <dkoloski@google.com>
* task: add consume_budget for cooperative scheduling
For cpu-only computations that do not use any Tokio resources,
budgeting does not really kick in in order to yield and prevent
other tasks from starvation. The new mechanism - consume_budget,
performs a budget check, consumes a unit of it, and yields only
if the task exceeded the budget. That allows cpu-intenstive
computations to define points in the program which indicate that
some significant work was performed. It will yield only if the budget
is gone, which is a much better alternative to unconditional yielding,
which is a potentially heavy operation.
* tests: add a test case for task::consume_budget
The test case ensures that the task::consume_budget utility
actually burns budget and makes the task yield once the whole
budget is gone.
Updating an atomic variable with a load followed by a store is racy. It
defeats the entire purpose of using atomic variables, and can result in
"lost" updates. Instead, use fetch_add .
Adds knobs to the runtime builder to control the number of ticks
between polling the global task queue (fairness) and the event driver
(I/O prioritization).
Both varieties of scheduler already supported these intervals, but they
were defined by private constants. Some workloads benefit from
customizing these values.
Closes#4651
## Motivation
Currently, the various spawning methods on `tokio::task::JoinSet` and
`tokio_util::task::JoinMap` lack `#[track_caller]` attributes, so the
`tracing` spans generated for tasks spawned on `JoinSet`s/`JoinMap`s
will have the `JoinSet` spawning method as their spawn location, rather
than the user code that called that method.
## Solution
This PR fixes that by...adding a bunch of `#[track_caller]` attributes.
## Future Work
In the future, we may also want to consider adding additional data to
the task span indicating that the task is spawned on a `JoinSet`...
Signed-off-by: Eliza Weisman <eliza@buoyant.io>
## Motivation
`task::JoinSet` currently has both `spawn`/`spawn_local` methods,
and `spawn_on`/`spawn_local_on` variants of these methods that take a
reference to a runtime `Handle` or to a `LocalSet`, and spawn tasks on
the provided runtime/`LocalSet`, rather than the current one. The
`task::Builder` type is _also_ an API type that can spawn tasks, but it
doesn't have `spawn_on` variants of its methods. It occurred to me that
it would be nice to have similar APIs on `task::Builder`.
## Solution
This branch adds `task::Builder::spawn_on`,
`task::Builder::spawn_local_on`, and `task::Builder::spawn_blocking_on`
methods, similar to those on `JoinSet`. In addition, I did some
refactoring of the internal spawning APIs --- there was a bit of
duplicated code that this PR reduces.
Signed-off-by: Eliza Weisman <eliza@buoyant.io>
This documents why it is safe to convert `bytes::UninitSlice` to `&mut
[MaybeUninit<u8>]`, and shrinks one of the unsafe blocks to make these
functions easier to audit.
Add a function that is more versatile than send_modify(). The result of
the passed closure indicates if the mutably borrowed value has actually
been modified or not. Receivers are only notified if the value has been
modified as indicated by the sender.
Signed-off-by: Uwe Klotz <uwe.klotz@slowtec.de>
