When a task holds a lock, it should not yield its time slice or it
should not be preempted out. In this way, we can mitigate harmful
preemption of lock holders and reduce the total preemption counts.
Signed-off-by: Changwoo Min <changwoo@igalia.com>
When a lock holder exhausts its time slide, it will be re-enqueued
to a DSQ waiting for shceduling while holding a lock. In this case,
prioritize its latency criticality proportionally, so a lock holder
would be not stuck in a DSQ for a long time, improving system-wide
progress.
Signed-off-by: Changwoo Min <changwoo@igalia.com>
Trace the acquisition and release of blocking locks for kernel and
fuxtexes for user-space. This is necessary to boost a lock holder
task in terms of latency and time slice. We do not boost shared
lock holders (e.g., read lock in rw_semaphore) since the kernel
already prioritizes the readers over writers.
Signed-off-by: Changwoo Min <changwoo@igalia.com>
In the WAKE_SYNC path lf L3 cache awareness is disabled (--disable-l3)
we may hit the following error:
Error: EXIT: scx_bpf_error (CPU L3 cpumask not initialized)
Fix this by setting the L3 cpumask to the whole primary domain if L3
cache awareness is disabled.
Tested-by: Eric Naim <dnaim@cachyos.org>
Signed-off-by: Andrea Righi <andrea.righi@linux.dev>
Refactor topology preemption logic so the non topology aware code is
contianed to a separate function. This should make maintaining the non
topology aware code path far easier.
Signed-off-by: Daniel Hodges <hodges.daniel.scott@gmail.com>
Rename the `load_adj` statistic to `load_frac_adj`, which is a more
accurate representation of what the statistic is calculating. The
statistic is a fractional representation of the load of a layer adjusted
for infeasible weights.
Signed-off-by: Daniel Hodges <hodges.daniel.scott@gmail.com>
Refactor layered_dispatch into two functions: layered_dispatch_no_topo and
layered_dispatch. layered_dispatch will delegate to layered_dispatch_no_topo in
the disable_topology case.
Although this code doesn't run when loaded by BPF due to the global constant
bool blocking it, it makes the functions really hard to parse as a human. As
they diverge more and more it makes sense to split them into separate
manageable functions.
This is basically a mechanical change. I duplicated the existing function,
replaced all `disable_topology` with true in `no_topo` and false in the
existing function, then removed all branches which can't be hit.
Test plan:
- Runs on my dev box (6.9.0 fbkernel) with `scx_layered --run-example -n`.
- As above with `-t`.
- CI.
clang is correctly warning that we use various uninitialised variables. clean
these up so real errors are easier to read.
The largest change here is to non-topological layered_dispatch. The
matching_dsq logic seems to be incorrect. It checks whether an uninitialised
variable is 0, if it is sets it, then only uses the variable if the value is 0.
I have changed this to default to -1, then use the value if it is no longer -1.
