Now that scheduling BPF timers works correctly, we don't need this extra
logic to eagerly compact if a scheduling for compaction has happened a
few times in a row. Let's remove it.
Signed-off-by: David Vernet <void@manifault.com>
In scx_nest, we use a per-cpu BPF timer to schedule compaction for a
primary core before it goes idle. If a task comes along that could use
that core, we cancel the callback with bpf_timer_cancel().
bpf_timer_cancel() drops a refcnt on the prog and nullifies the
callback, so if we want to schedule the callback again, we must use
bpf_timer_set_callback() to reset the prog. This patch does that.
Reported-by: Julia Lawall <julia.lawall@inria.fr>
Signed-off-by: David Vernet <void@manifault.com>
In the latest kernel, sched_ext API has changed in two areas:
- ops.prep_enable/cancel_enable/enable/disable() replaced with
ops.init_task/enable/disable/exit_task().
- scx_bpf_dispatch() can now be called from ops.select_cpu(). Also,
SCX_ENQ_LOCAL flag is removed. Instead, users can call
scx_bpf_select_cpu_dfl() from ops.select_cpu() and use the @is_idle out
param value to determine whether to dispatch directly.
This commit updates all schedules so that they build.
- Init functions renamed / merged / split.
- ops.select_cpu() is added to several schedulers and local direct
disptching logic is moved there.
This is the minimum update which is need to make the schedulers build and
work. It needs further update to e.g. move vtime udpates to ops.enable().
The core sched code calls select_task_rq() in a few places: the task
wakeup path (typical path), the fork() path, and the exec() path. For
nest scheduling, we don't want to select a core from the nest on the
exec() path. If we were previously able to find an idle core, we would
have found it on the fork() path, so we don't gain much by checking on
the exec() path. In fact, it's actually harmful, because we could
incorrectly blow up the primary nest unnecessarily by bumping the same
task between multiple cores for no reason. Let's just opt-out of
select_task_rq calls on the exec() path.
Suggested-by: Julia Lawall <julia.lawall@inria.fr>
Signed-off-by: David Vernet <void@manifault.com>
Julia pointed out that our current implementation of r_impatient is
incorrect. r_impatient is meant to be a mechanism for more aggressively
growing the primary nest if a task repeatedly isn't able to find a core.
Right now, we trigger r_impatient if we're not able to find an attached
or previous core in the primary nest, but we _should_ be triggering it
only if we're unable to find _any_ core in the primary nest. Fixing the
implementation to do this drastically decreases how aggressively we grow
the primary nest when r_impatient is in effect.
Reported-by: Julia Lawall <julia.lawall@inria.fr>
Signed-off-by: David Vernet <void@manifault.com>
- combine c and kernel-examples as it's confusing to have both
- rename 'rust-user' and 'c-user' to just 'rust' and 'c', which is simpler
- update and fix sync-to-kernel.sh
