pm24.git/Documentation/scheduler, branch master

sched_ext: Rename scx_bpf_consume() to scx_bpf_dsq_move_to_local()

2024-11-11T17:06:16Z

In sched_ext API, a repeatedly reported pain point is the overuse of the verb "dispatch" and confusion around "consume": - ops.dispatch() - scx_bpf_dispatch[_vtime]() - scx_bpf_consume() - scx_bpf_dispatch[_vtime]_from_dsq*() This overloading of the term is historical. Originally, there were only built-in DSQs and moving a task into a DSQ always dispatched it for execution. Using the verb "dispatch" for the kfuncs to move tasks into these DSQs made sense. Later, user DSQs were added and scx_bpf_dispatch[_vtime]() updated to be able to insert tasks into any DSQ. The only allowed DSQ to DSQ transfer was from a non-local DSQ to a local DSQ and this operation was named "consume". This was already confusing as a task could be dispatched to a user DSQ from ops.enqueue() and then the DSQ would have to be consumed in ops.dispatch(). Later addition of scx_bpf_dispatch_from_dsq*() made the confusion even worse as "dispatch" in this context meant moving a task to an arbitrary DSQ from a user DSQ. Clean up the API with the following renames: 1. scx_bpf_dispatch[_vtime]() -> scx_bpf_dsq_insert[_vtime]() 2. scx_bpf_consume() -> scx_bpf_dsq_move_to_local() 3. scx_bpf_dispatch[_vtime]_from_dsq*() -> scx_bpf_dsq_move[_vtime]*() This patch performs the second rename. Compatibility is maintained by: - The previous kfunc names are still provided by the kernel so that old binaries can run. Kernel generates a warning when the old names are used. - compat.bpf.h provides wrappers for the new names which automatically fall back to the old names when running on older kernels. They also trigger build error if old names are used for new builds. The compat features will be dropped after v6.15. v2: Comment and documentation updates. Signed-off-by: Tejun Heo Acked-by: Andrea Righi Acked-by: Changwoo Min Acked-by: Johannes Bechberger Acked-by: Giovanni Gherdovich Cc: Dan Schatzberg Cc: Ming Yang

sched_ext: Rename scx_bpf_dispatch[_vtime]() to scx_bpf_dsq_insert[_vtime]()

2024-11-11T17:06:16Z

In sched_ext API, a repeatedly reported pain point is the overuse of the verb "dispatch" and confusion around "consume": - ops.dispatch() - scx_bpf_dispatch[_vtime]() - scx_bpf_consume() - scx_bpf_dispatch[_vtime]_from_dsq*() This overloading of the term is historical. Originally, there were only built-in DSQs and moving a task into a DSQ always dispatched it for execution. Using the verb "dispatch" for the kfuncs to move tasks into these DSQs made sense. Later, user DSQs were added and scx_bpf_dispatch[_vtime]() updated to be able to insert tasks into any DSQ. The only allowed DSQ to DSQ transfer was from a non-local DSQ to a local DSQ and this operation was named "consume". This was already confusing as a task could be dispatched to a user DSQ from ops.enqueue() and then the DSQ would have to be consumed in ops.dispatch(). Later addition of scx_bpf_dispatch_from_dsq*() made the confusion even worse as "dispatch" in this context meant moving a task to an arbitrary DSQ from a user DSQ. Clean up the API with the following renames: 1. scx_bpf_dispatch[_vtime]() -> scx_bpf_dsq_insert[_vtime]() 2. scx_bpf_consume() -> scx_bpf_dsq_move_to_local() 3. scx_bpf_dispatch[_vtime]_from_dsq*() -> scx_bpf_dsq_move[_vtime]*() This patch performs the first set of renames. Compatibility is maintained by: - The previous kfunc names are still provided by the kernel so that old binaries can run. Kernel generates a warning when the old names are used. - compat.bpf.h provides wrappers for the new names which automatically fall back to the old names when running on older kernels. They also trigger build error if old names are used for new builds. The compat features will be dropped after v6.15. v2: Documentation updates. Signed-off-by: Tejun Heo Acked-by: Andrea Righi Acked-by: Changwoo Min Acked-by: Johannes Bechberger Acked-by: Giovanni Gherdovich Cc: Dan Schatzberg Cc: Ming Yang

sched_ext: Documentation: Update instructions for running example schedulers

2024-10-08T18:49:18Z

Since the artifact paths for tools changed, we need to update the documentation to reflect that path. Signed-off-by: Devaansh-Kumar Signed-off-by: Tejun Heo

sched_ext: Provide a sysfs enable_seq counter

2024-09-23T16:53:02Z

As discussed during the distro-centric session within the sched_ext Microconference at LPC 2024, introduce a sequence counter that is incremented every time a BPF scheduler is loaded. This feature can help distributions in diagnosing potential performance regressions by identifying systems where users are running (or have ran) custom BPF schedulers. Example: arighi@virtme-ng~> cat /sys/kernel/sched_ext/enable_seq 0 arighi@virtme-ng~> sudo scx_simple local=1 global=0 ^CEXIT: unregistered from user space arighi@virtme-ng~> cat /sys/kernel/sched_ext/enable_seq 1 In this way user-space tools (such as Ubuntu's apport and similar) are able to gather and include this information in bug reports. Cc: Giovanni Gherdovich Cc: Kleber Sacilotto de Souza Cc: Marcelo Henrique Cerri Cc: Phil Auld Signed-off-by: Andrea Righi Signed-off-by: Tejun Heo

Merge tag 'sched_ext-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

2024-09-21T16:44:57Z

Pull sched_ext support from Tejun Heo: "This implements a new scheduler class called ‘ext_sched_class’, or sched_ext, which allows scheduling policies to be implemented as BPF programs. The goals of this are: - Ease of experimentation and exploration: Enabling rapid iteration of new scheduling policies. - Customization: Building application-specific schedulers which implement policies that are not applicable to general-purpose schedulers. - Rapid scheduler deployments: Non-disruptive swap outs of scheduling policies in production environments" See individual commits for more documentation, but also the cover letter for the latest series: Link: https://lore.kernel.org/all/20240618212056.2833381-1-tj@kernel.org/ * tag 'sched_ext-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (110 commits) sched: Move update_other_load_avgs() to kernel/sched/pelt.c sched_ext: Don't trigger ops.quiescent/runnable() on migrations sched_ext: Synchronize bypass state changes with rq lock scx_qmap: Implement highpri boosting sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq() sched_ext: Compact struct bpf_iter_scx_dsq_kern sched_ext: Replace consume_local_task() with move_local_task_to_local_dsq() sched_ext: Move consume_local_task() upward sched_ext: Move sanity check and dsq_mod_nr() into task_unlink_from_dsq() sched_ext: Reorder args for consume_local/remote_task() sched_ext: Restructure dispatch_to_local_dsq() sched_ext: Fix processs_ddsp_deferred_locals() by unifying DTL_INVALID handling sched_ext: Make find_dsq_for_dispatch() handle SCX_DSQ_LOCAL_ON sched_ext: Refactor consume_remote_task() sched_ext: Rename scx_kfunc_set_sleepable to unlocked and relocate sched_ext: Add missing static to scx_dump_data sched_ext: Add missing static to scx_has_op[] sched_ext: Temporarily work around pick_task_scx() being called without balance_scx() sched_ext: Add a cgroup scheduler which uses flattened hierarchy sched_ext: Add cgroup support ...

Merge tag 'sched-core-2024-09-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2024-09-19T13:55:58Z

Pull scheduler updates from Ingo Molnar: - Implement the SCHED_DEADLINE server infrastructure - Daniel Bristot de Oliveira's last major contribution to the kernel: "SCHED_DEADLINE servers can help fixing starvation issues of low priority tasks (e.g., SCHED_OTHER) when higher priority tasks monopolize CPU cycles. Today we have RT Throttling; DEADLINE servers should be able to replace and improve that." (Daniel Bristot de Oliveira, Peter Zijlstra, Joel Fernandes, Youssef Esmat, Huang Shijie) - Preparatory changes for sched_ext integration: - Use set_next_task(.first) where required - Fix up set_next_task() implementations - Clean up DL server vs. core sched - Split up put_prev_task_balance() - Rework pick_next_task() - Combine the last put_prev_task() and the first set_next_task() - Rework dl_server - Add put_prev_task(.next) (Peter Zijlstra, with a fix by Tejun Heo) - Complete the EEVDF transition and refine EEVDF scheduling: - Implement delayed dequeue - Allow shorter slices to wakeup-preempt - Use sched_attr::sched_runtime to set request/slice suggestion - Document the new feature flags - Remove unused and duplicate-functionality fields - Simplify & unify pick_next_task_fair() - Misc debuggability enhancements (Peter Zijlstra, with fixes/cleanups by Dietmar Eggemann, Valentin Schneider and Chuyi Zhou) - Initialize the vruntime of a new task when it is first enqueued, resulting in significant decrease in latency of newly woken tasks (Zhang Qiao) - Introduce SM_IDLE and an idle re-entry fast-path in __schedule() (K Prateek Nayak, Peter Zijlstra) - Clean up and clarify the usage of Clean up usage of rt_task() (Qais Yousef) - Preempt SCHED_IDLE entities in strict cgroup hierarchies (Tianchen Ding) - Clarify the documentation of time units for deadline scheduler parameters (Christian Loehle) - Remove the HZ_BW chicken-bit feature flag introduced a year ago, the original change seems to be working fine (Phil Auld) - Misc fixes and cleanups (Chen Yu, Dan Carpenter, Huang Shijie, Peilin He, Qais Yousefm and Vincent Guittot) * tag 'sched-core-2024-09-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (64 commits) sched/cpufreq: Use NSEC_PER_MSEC for deadline task cpufreq/cppc: Use NSEC_PER_MSEC for deadline task sched/deadline: Clarify nanoseconds in uapi sched/deadline: Convert schedtool example to chrt sched/debug: Fix the runnable tasks output sched: Fix sched_delayed vs sched_core kernel/sched: Fix util_est accounting for DELAY_DEQUEUE kthread: Fix task state in kthread worker if being frozen sched/pelt: Use rq_clock_task() for hw_pressure sched/fair: Move effective_cpu_util() and effective_cpu_util() in fair.c sched/core: Introduce SM_IDLE and an idle re-entry fast-path in __schedule() sched: Add put_prev_task(.next) sched: Rework dl_server sched: Combine the last put_prev_task() and the first set_next_task() sched: Rework pick_next_task() sched: Split up put_prev_task_balance() sched: Clean up DL server vs core sched sched: Fixup set_next_task() implementations sched: Use set_next_task(.first) where required sched/fair: Properly deactivate sched_delayed task upon class change ...

Merge branch 'tip/sched/core' into sched_ext/for-6.12

2024-09-11T18:43:26Z

Pull in tip/sched/core to resolve two merge conflicts: - 96fd6c65efc6 ("sched: Factor out update_other_load_avgs() from __update_blocked_others()") 5d871a63997f ("sched/fair: Move effective_cpu_util() and effective_cpu_util() in fair.c") A simple context conflict. The former added __update_blocked_others() in the same #ifdef CONFIG_SMP block that effective_cpu_util() and sched_cpu_util() are in and the latter moved those functions to fair.c. This makes __update_blocked_others() more out of place. Will follow up with a patch to relocate. - 96fd6c65efc6 ("sched: Factor out update_other_load_avgs() from __update_blocked_others()") 84d265281d6c ("sched/pelt: Use rq_clock_task() for hw_pressure") The former factored out the body of __update_blocked_others() into update_other_load_avgs(). The latter changed how update_hw_load_avg() is called in the body. Resolved by applying the change to update_other_load_avgs() instead. Signed-off-by: Tejun Heo

sched/deadline: Convert schedtool example to chrt

2024-09-11T09:23:56Z

chrt has SCHED_DEADLINE support so convert the example instead of relying on a schedtool fork. While at it fix the wrong mentioning of microseconds, it was nanoseconds for both schedtool and chrt. Signed-off-by: Christian Loehle Signed-off-by: Peter Zijlstra (Intel) Acked-by: Juri Lelli Acked-by: Rafael J. Wysocki Link: https://lore.kernel.org/r/20240813144348.1180344-2-christian.loehle@arm.com

docs: scheduler: completion: Update member of struct completion

2024-09-05T20:17:45Z

The member "wait" in struct completion isn't of type wait_queue_head_t anymore, as it is now "struct swait_queue_head", fix it to match with the current implementation. Signed-off-by: I Hsin Cheng Reviewed-by: Kuan-Wei Chiu Signed-off-by: Jonathan Corbet Link: https://lore.kernel.org/r/20240828165036.178011-1-richard120310@gmail.com

docs: scheduler: Start documenting the EEVDF scheduler

2024-08-07T19:37:16Z

Add some documentation regarding the newly introduced scheduler EEVDF. Signed-off-by: Carlos Bilbao Signed-off-by: Jonathan Corbet Link: https://lore.kernel.org/r/20240720002207.444286-2-carlos.bilbao.osdev@gmail.com