Provide distinct methods to set the target CPU and the per-task time
slice to dispatched tasks.
Moreover, also provide a constructor to create a DispatchedTask from a
QueuedTask (this allows to automatically bounce a task from the
scheduler to the BPF dispatcher without having to take care of setting
the individual task's attributes).
This also allows to make most of the attributes of DispatchedTask
private, especially it allows to hide cpumask_cnt, that should be only
used internally between the BPF and the user-space component.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Provide a way to set a different time slice per-task, by adding a new
attribute slice_ns to the DispatchedTask struct.
This attribute determines the time slice assigned to the task, if it is
set to 0 then the global time slice (either the default one or the
effective one, if set) will be used.
At the same time, remove the payload attribute, that is basically unused
(scx_rustland uses it to send the task's vruntime to the BPF dispatcher
for debugging purposes, but it's not very useful anymore at this point).
In the future we may introduce a proper interface to attach a custom
payload to each task with a proper interface.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
This is to potentinally reduce issues with folks
using different versions of libbpf at runtime.
This also:
- makes static linking of libbpf the default
- adds steps in `meson setup` to fetch libbpf and make it
This reverts commit a7b39f24e2, reversing
changes made to cf7404fb03.
The PR doesn't do what the description says. It instead limits the number of
rustc instances to 1 for each cargo build making rust builds extremely slow.
Let's revert and try again.
This reverts commit 5b9b953e3c, reversing
changes made to a7b39f24e2.
The current git submodule approach is a bit cumbersome and doesn't provide a
unified build environment for both libbpf and scx scheds. Also, the build
instruction doesn't seem to work. Let's revert it for now.
Each cargo build is already parallelized, spreading multiple rustc
across all the available CPUs by default.
Allowing to run multiple instances of cargo at the same time doesn't
provide any benefit and it can only increase the risk of triggering OOM
conditions or overloading the build system.
Therefore, limit the amount of parallel cargo build instances to 1.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
There is no need to generate source code in a temporary directory with
RustLandBuilder(), we can simply generate code in-tree and exclude the
generated source files from .gitignore.
Having the generated source files in-tree can help to debug potential
build issues (and it also allows to drop the the tempfile crate
dependency).
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Introduce a Builder() class in scx_utils that can be used by other scx
crates (such as scx_rustland_core) to prevent code duplication.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Introduce a wrapper to scx_utils::BpfBuilder that can be used to build
the BPF component provided by scx_rustland_core.
The source of the BPF components (main.bpf.c) is included in the crate
as an array of bytes, the content is then unpacked in a temporary file
to perform the build.
The RustLandBuilder() helper is also used to generate bpf.rs (that
implements the low-level user-space Rust connector to the BPF
commponent).
Schedulers based on scx_rustland_core can simply use RustLandBuilder(),
to build the backend provided by scx_rustland_core.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Introduce a helper function to update the counter of queued and
scheduled tasks (used to notify the BPF component if the user-space
scheduler has still some pending work to do).
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
scx_rustland has significantly evolved since its original design.
With the introduction of scx_rustland_core and the inclusion of the
scx_rlfifo example, scx_rustland's focus can be shifted from solely
being an "easy-to-read Rust scheduler template" to a fully functional
scheduler.
For this reason, update the README and documentation to reflect its
revised design, objectives, and intended use cases.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Move the BPF component of scx_rustland to scx_rustland_core and make it
available to other user-space schedulers.
NOTE: main.bpf.c and bpf.rs are not pre-compiled in the
scx_rustland_core crate, they need to be included in the user-space
scheduler's source code in order to be compiled/linked properly.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Introduce a separate crate (scx_rustland_core) that can be used to
implement sched-ext schedulers in Rust that run in user-space.
This commit only provides the basic layout for the new crate and the
abstraction to the custom allocator.
In general, any scheduler that has a user-space component needs to use
the custom allocator to prevent potential deadlock conditions, caused by
page faults (a kthread needs to run to resolve the page fault, but the
scheduler is blocked waiting for the user-space page fault to be
resolved => deadlock).
However, we don't want to necessarily enforce this constraint to all the
existing Rust schedulers, some of them may do all user-space allocations
in safe paths, hence the separate scx_rustland_core crate.
Merging this code in scx_utils would force all the Rust schedulers to
use the custom allocator.
In a future commit the scx_rustland backend will be moved to
scx_rustland_core, making it a totally generic BPF scheduler framework
that can be used to implement user-space schedulers in Rust.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Now that we have a new 'infeasible' crate that abstracts the logic for
implementing the infeasible weights solution. Let's update rusty to use
it.
Signed-off-by: David Vernet <void@manifault.com>
We want to avoid every scheduler implementation from having to implement
the solution to the infeasible weights problem, but we also want to
enable sufficient flexibility where not every program has to have the
same partition of scheduling domains, etc. To enable this, a new
infeasible crate is added which encapsulates all of the logic for being
given duty cycle and weight, and performing the necessary math to adjust
for infeasibility.
Signed-off-by: David Vernet <void@manifault.com>
These two schedulers are provided mostly as examples / PoC, so we should
exclude them from our periodic testing, to prevent triggering false
positives in our CI.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
The new topology crate allows us to replace the custom rustland topology
logic with the logic in the topology crate itself.
Signed-off-by: David Vernet <void@manifault.com>
For convenience, let's provide callers with a way to easily look up
cores and CPUs from the root topology object.
Signed-off-by: David Vernet <void@manifault.com>
The topology.rs crate is insufficiently generic, and reflects
implementation details of scx_rusty more than it provides generic use
cases for modeling a host's topology. This adds a new topology2.rs crate
that will replace topology.rs. We have this as an intermediate commit so
that we don't bundle updating scx_rusty with adding this crate.
Signed-off-by: David Vernet <void@manifault.com>
Now that we have cpumask.rs, we can remove some logic from topology.rs
and have it create and use Cpumasks.
Signed-off-by: David Vernet <void@manifault.com>
Let's add a Cpumask trait that schedulers can use to avoid all having to
deal directly with BitVec and the like.
Signed-off-by: David Vernet <void@manifault.com>
I have a usecase where specific nice values are used to bucket tasks
into groups that are handled separately by different `scx_layered`
policies, with no implications of relative priority between niceness X,
X + 1, X - 1, etc. In other words, nicevals are used as simple tags in
this scenario.
If we wanted to treat a specific niceness this way e.g. `11`, we could
do so with AND'd MATCH_NICE_{ABOVE,BELOW} like so:
```json
"matches" : [
[
{
"NiceAbove": 10
},
{
"NiceBelow": 12
},
],
],
```
But this is unnecessarily verbose and doesn't communicate the intent of
the match very well. Adding a `NiceEquals` matcher simplifies the
config and makes intent obvious:
```json
"matches" : [
[
{
"NiceEquals": 11
},
],
],
```
This PR adds support for such a matcher.
Also, rename `layer_match.nice_above_or_below` to just
`layer_match.nice`, as the former doesn't describe the newly-added
matcher's use of the field. It's still obvious that `layer_match.nice`
is relevant to MATCH_NICE_{ABOVE, BELOW, EQUALS}.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
As mentioned in the previous commit, for some reason we're sometimes
(non-deterministically) not seeing the updated cpumask / layer values in
BPF if we initialize the cpumasks here before attaching. Let's undo this
for now so to avoid observing buggy behavior, until we figure it out.
Signed-off-by: David Vernet <void@manifault.com>
This reverts commit 56ff3437a2.
For some reason we seem to be non-deterministically failing to see the
updated layer values in BPF if we initialize before attaching. Let's
just undo this specific part so that we can unblock this being broken,
and we can figure it out async.
Signed-off-by: David Vernet <void@manifault.com>
