linux-toradex.git/include/linux/sched/topology.h, branch v6.17

sched/topology: Remove sched_domain_topology_level::flags

2025-07-14T08:59:35+00:00

Support for overlapping domains added in commit e3589f6c81e4 ("sched:
Allow for overlapping sched_domain spans") also allowed forcefully
setting SD_OVERLAP for !NUMA domains via FORCE_SD_OVERLAP sched_feat().

Since NUMA domains had to be presumed overlapping to ensure correct
behavior, "sched_domain_topology_level::flags" was introduced. NUMA
domains added the SDTL_OVERLAP flag would ensure SD_OVERLAP was always
added during build_sched_domains() for these domains, even when
FORCE_SD_OVERLAP was off.

Condition for adding the SD_OVERLAP flag at the aforementioned commit
was as follows:

    if (tl->flags & SDTL_OVERLAP || sched_feat(FORCE_SD_OVERLAP))
            sd->flags |= SD_OVERLAP;

The FORCE_SD_OVERLAP debug feature was removed in commit af85596c74de
("sched/topology: Remove FORCE_SD_OVERLAP") which left the NUMA domains
as the exclusive users of SDTL_OVERLAP, SD_OVERLAP, and SD_NUMA flags.

Get rid of SDTL_OVERLAP and SD_OVERLAP as they have become redundant
and instead rely on SD_NUMA to detect the only overlapping domain
currently supported. Since SDTL_OVERLAP was the only user of
"tl->flags", get rid of "sched_domain_topology_level::flags" too.

Signed-off-by: K Prateek Nayak 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/ba4dbdf8-bc37-493d-b2e0-2efb00ea3e19@amd.com

smpboot: introduce SDTL_INIT() helper to tidy sched topology setup

2025-07-14T08:59:34+00:00

Define a small SDTL_INIT(maskfn, flagsfn, name) macro and use it to build the
sched_domain_topology_level array. Purely a cleanup; behaviour is unchanged.

Suggested-by: Thomas Gleixner 
Signed-off-by: Li Chen 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: K Prateek Nayak 
Tested-by: K Prateek Nayak 
Link: https://lore.kernel.org/r/20250710105715.66594-2-me@linux.beauty

sched/smp: Make SMP unconditional

2025-06-13T06:47:18+00:00

Simplify the scheduler by making CONFIG_SMP=y primitives and data
structures unconditional.

Introduce transitory wrappers for functionality not yet converted to SMP.

Note that this patch is pretty large, because there's no clear separation
between various aspects of the SMP scheduler, it's basically a huge block
of #ifdef CONFIG_SMP. A fair amount of it has to be switched on for it to
boot and work on UP systems.

Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Cc: Dietmar Eggemann 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Mel Gorman 
Cc: Sebastian Andrzej Siewior 
Cc: Shrikanth Hegde 
Cc: Steven Rostedt 
Cc: Valentin Schneider 
Cc: Vincent Guittot 
Link: https://lore.kernel.org/r/20250528080924.2273858-21-mingo@kernel.org

sched/topology: Introduce sched_update_asym_prefer_cpu()

2025-04-16T19:09:11+00:00

A subset of AMD Processors supporting Preferred Core Rankings also
feature the ability to dynamically switch these rankings at runtime to
bias load balancing towards or away from the LLC domain with larger
cache.

To support dynamically updating "sg->asym_prefer_cpu" without needing to
rebuild the sched domain, introduce sched_update_asym_prefer_cpu() which
recomutes the "asym_prefer_cpu" when the core-ranking of a CPU changes.

sched_update_asym_prefer_cpu() swaps the "sg->asym_prefer_cpu" with the
CPU whose ranking has changed if the new ranking is greater than that of
the "asym_prefer_cpu". If CPU whose ranking has changed is the current
"asym_prefer_cpu", it scans the CPUs of the sched groups to find the new
"asym_prefer_cpu" and sets it accordingly.

get_group() for non-overlapping sched domains returns the sched group
for the first CPU in the sched_group_span() which ensures all CPUs in
the group see the updated value of "asym_prefer_cpu".

Overlapping groups are allocated differently and will require moving the
"asym_prefer_cpu" to "sg->sgc" but since the current implementations do
not set "SD_ASYM_PACKING" at NUMA domains, skip additional
indirection and place a SCHED_WARN_ON() to alert any future users.

Signed-off-by: K Prateek Nayak 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20250409053446.23367-3-kprateek.nayak@amd.com

sched/debug: Make CONFIG_SCHED_DEBUG functionality unconditional

2025-03-19T21:20:53+00:00

All the big Linux distros enable CONFIG_SCHED_DEBUG, because
the various features it provides help not just with kernel
development, but with system administration and user-space
software development as well.

Reflect this reality and enable this functionality
unconditionally.

Signed-off-by: Ingo Molnar 
Tested-by: Shrikanth Hegde 
Cc: Peter Zijlstra 
Cc: Juri Lelli 
Cc: Vincent Guittot 
Cc: Dietmar Eggemann 
Cc: Steven Rostedt 
Cc: Ben Segall 
Cc: Mel Gorman 
Cc: Valentin Schneider 
Cc: Linus Torvalds 
Link: https://lore.kernel.org/r/20250317104257.3496611-4-mingo@kernel.org

include/{topology,cpuset}: Move dl_rebuild_rd_accounting to cpuset.h

2025-03-17T10:23:43+00:00

dl_rebuild_rd_accounting() is defined in cpuset.c, so it makes more
sense to move related declarations to cpuset.h.

Implement the move.

Suggested-by: Waiman Long 
Signed-off-by: Juri Lelli 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Waiman Long 
Reviewed-by: Valentin Schneider 
Reviewed-by: Dietmar Eggemann 
Tested-by: Waiman Long 
Tested-by: Jon Hunter 
Tested-by: Dietmar Eggemann 
Link: https://lore.kernel.org/r/Z9MSOVMpU7jpVrMU@jlelli-thinkpadt14gen4.remote.csb

sched/topology: Stop exposing partition_sched_domains_locked

2025-03-17T10:23:43+00:00

The are no callers of partition_sched_domains_locked() outside
topology.c.

Stop exposing such function.

Suggested-by: Waiman Long 
Signed-off-by: Juri Lelli 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Valentin Schneider 
Reviewed-by: Dietmar Eggemann 
Tested-by: Waiman Long 
Tested-by: Jon Hunter 
Tested-by: Dietmar Eggemann 
Link: https://lore.kernel.org/r/Z9MSC96a8FcqWV3G@jlelli-thinkpadt14gen4.remote.csb

sched/deadline: Rebuild root domain accounting after every update

2025-03-17T10:23:42+00:00

Rebuilding of root domains accounting information (total_bw) is
currently broken on some cases, e.g. suspend/resume on aarch64. Problem
is that the way we keep track of domain changes and try to add bandwidth
back is convoluted and fragile.

Fix it by simplify things by making sure bandwidth accounting is cleared
and completely restored after root domains changes (after root domains
are again stable).

To be sure we always call dl_rebuild_rd_accounting while holding
cpuset_mutex we also add cpuset_reset_sched_domains() wrapper.

Fixes: 53916d5fd3c0 ("sched/deadline: Check bandwidth overflow earlier for hotplug")
Reported-by: Jon Hunter 
Co-developed-by: Waiman Long 
Signed-off-by: Waiman Long 
Signed-off-by: Juri Lelli 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Dietmar Eggemann 
Tested-by: Dietmar Eggemann 
Link: https://lore.kernel.org/r/Z9MRfeJKJUOyUSto@jlelli-thinkpadt14gen4.remote.csb

sched: Move sched domain name out of CONFIG_SCHED_DEBUG

2024-12-20T14:31:17+00:00

/proc/schedstat file shows cpu and sched domain level scheduler
statistics. It does not show domain name instead shows domain level.
It will be very useful for tools like `perf sched stats`[1] to
aggragate domain level stats if domain names are shown in /proc/schedstat.
But sched domain name is guarded by CONFIG_SCHED_DEBUG. As per the
discussion[2], move sched domain name out of CONFIG_SCHED_DEBUG.

[1] https://lore.kernel.org/lkml/20241122084452.1064968-1-swapnil.sapkal@amd.com/
[2] https://lore.kernel.org/lkml/fcefeb4d-3acb-462d-9c9b-3df8d927e522@amd.com/

Suggested-by: "Gautham R. Shenoy" 
Signed-off-by: Swapnil Sapkal 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20241220063224.17767-5-swapnil.sapkal@amd.com

sched: Report the different kinds of imbalances in /proc/schedstat

2024-12-20T14:31:17+00:00

In /proc/schedstat, lb_imbalance reports the sum of imbalances
discovered in sched domains with each call to sched_balance_rq(), which is
not very useful because lb_imbalance does not mention whether the imbalance
is due to load, utilization, nr_tasks or misfit_tasks. Remove this field
from /proc/schedstat.

Currently there is no field in /proc/schedstat to report different types
of imbalances. Introduce new fields in /proc/schedstat to report the
total imbalances in load, utilization, nr_tasks or misfit_tasks.

Added fields to /proc/schedstat:
        - lb_imbalance_load: Total imbalance due to load.
        - lb_imbalance_util: Total imbalance due to utilization.
        - lb_imbalance_task: Total imbalance due to number of tasks.
        - lb_imbalance_misfit: Total imbalance due to misfit tasks.

Signed-off-by: Swapnil Sapkal 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Shrikanth Hegde 
Link: https://lore.kernel.org/r/20241220063224.17767-4-swapnil.sapkal@amd.com