linux-toradex.git/tools/sched_ext/Makefile, branch master

tools/sched_ext: Add -fms-extensions to bpf build flags

2026-03-03T08:00:23+00:00

Similar to commit 835a50753579 ("selftests/bpf: Add -fms-extensions to
bpf build flags") and commit 639f58a0f480 ("bpftool: Fix build warnings
due to MS extensions")

The kernel is now built with -fms-extensions, therefore
generated vmlinux.h contains types like:
struct aes_key {
        struct aes_enckey;
        union aes_invkey_arch inv_k;
};

struct ns_common {
	...
        union {
                struct ns_tree;
                struct callback_head ns_rcu;
        };
};

Which raise warning like below when building scx scheduler:

tools/sched_ext/build/include/vmlinux.h:50533:3: warning:
declaration does not declare anything [-Wmissing-declarations]
 50533 |                 struct ns_tree;
       |                 ^
Fix it by using -fms-extensions and -Wno-microsoft-anon-tag flags
to build bpf programs that #include "vmlinux.h"

Signed-off-by: Zhao Mengmeng 
Reviewed-by: Andrea Righi 
Signed-off-by: Tejun Heo

tools/sched_ext: add arena based scheduler

2026-01-28T01:43:34+00:00

Add a scheduler that uses BPF arenas to manage task context data.

Signed-off-by: Emil Tsalapatis 
Signed-off-by: Tejun Heo

tools/sched_ext: add scx_pair scheduler

2026-01-28T01:43:28+00:00

Add the scx_pair cgroup-based core scheduler.

Cc: Tejun Heo 
Cc: David Vernet 
Signed-off-by: Emil Tsalapatis 
Signed-off-by: Tejun Heo

tools/sched_ext: add scx_userland scheduler

2026-01-28T01:43:22+00:00

Add in the scx_userland scheduler that does vruntime-based
scheduling in userspace code and communicates scheduling
decisions to BPF by accessing and modifying globals through
the skeleton.

Cc: Tejun Heo 
Cc: David Vernet 
Signed-off-by: Emil Tsalapatis 
Signed-off-by: Tejun Heo

sched_ext: tools: Removing duplicate targets during non-cross compilation

2025-11-20T17:00:27+00:00

When cross-compilation is not used, BPFOBJ and HOST_BPFOBJ are identical
files, libbpf.a, and duplicate libbpf.a files should be removed.

Signed-off-by: Rong Tao 
Signed-off-by: Tejun Heo

sched_ext: Add scx_cpu0 example scheduler

2025-11-12T16:43:44+00:00

Add scx_cpu0, a simple scheduler that queues all tasks to a single DSQ and
only dispatches them from CPU0 in FIFO order. This is useful for testing bypass
behavior when many tasks are concentrated on a single CPU. If the load balancer
doesn't work, bypass mode can trigger task hangs or RCU stalls as the queue is
long and there's only one CPU working on it.

v2: Check whether task is on CPU0 at enqueue using scx_bpf_task_cpu() instead
    of nr_cpus_allowed (Andrea Righi).

Cc: Dan Schatzberg 
Cc: Emil Tsalapatis 
Reviewed-by: Andrea Righi 
Signed-off-by: Tejun Heo

sched_ext: Improve cross-compilation support in Makefile

2025-04-14T16:58:41+00:00

Modify the tools/sched_ext/Makefile to better handle cross-compilation
environments by:

1. Fix host tools build directory structure by separating obj/ from output
   (HOST_BUILD_DIR now points to $(OBJ_DIR)/host/obj)
2. Properly propagate CROSS_COMPILE to libbpf sub-make invocation
3. Add missing $(HOST_BPFOBJ) build rule with proper host toolchain flags
   (ARCH=, CROSS_COMPILE=, explicit HOSTCC/HOSTLD)
4. Consistently quote $(HOSTCC) in bpftool build rule
5. Change LDFLAGS assignment to += to allow external extensions

The changes ensure proper cross-compilation behavior while maintaining
backward compatibility with native builds. Host tools are now correctly
built with the host toolchain while target binaries use the cross-toolchain.

Signed-off-by: yangsonghua 
Signed-off-by: Tejun Heo

sched_ext: Add a cgroup scheduler which uses flattened hierarchy

2024-09-04T20:24:59+00:00

This patch adds scx_flatcg example scheduler which implements hierarchical
weight-based cgroup CPU control by flattening the cgroup hierarchy into a
single layer by compounding the active weight share at each level.

This flattening of hierarchy can bring a substantial performance gain when
the cgroup hierarchy is nested multiple levels. in a simple benchmark using
wrk[8] on apache serving a CGI script calculating sha1sum of a small file,
it outperforms CFS by ~3% with CPU controller disabled and by ~10% with two
apache instances competing with 2:1 weight ratio nested four level deep.

However, the gain comes at the cost of not being able to properly handle
thundering herd of cgroups. For example, if many cgroups which are nested
behind a low priority parent cgroup wake up around the same time, they may
be able to consume more CPU cycles than they are entitled to. In many use
cases, this isn't a real concern especially given the performance gain.
Also, there are ways to mitigate the problem further by e.g. introducing an
extra scheduling layer on cgroup delegation boundaries.

v5: - Updated to specify SCX_OPS_HAS_CGROUP_WEIGHT instead of
      SCX_OPS_KNOB_CGROUP_WEIGHT.

v4: - Revert reference counted kptr for cgv_node as the change caused easily
      reproducible stalls.

v3: - Updated to reflect the core API changes including ops.init/exit_task()
      and direct dispatch from ops.select_cpu(). Fixes and improvements
      including additional statistics.

    - Use reference counted kptr for cgv_node instead of xchg'ing against
      stash location.

    - Dropped '-p' option.

v2: - Use SCX_BUG[_ON]() to simplify error handling.

Signed-off-by: Tejun Heo 
Reviewed-by: David Vernet 
Acked-by: Josh Don 
Acked-by: Hao Luo 
Acked-by: Barret Rhoden

sched_ext: Add a central scheduler which makes all scheduling decisions on one CPU

2024-06-18T20:09:19+00:00

This patch adds a new example scheduler, scx_central, which demonstrates
central scheduling where one CPU is responsible for making all scheduling
decisions in the system using scx_bpf_kick_cpu(). The central CPU makes
scheduling decisions for all CPUs in the system, queues tasks on the
appropriate local dsq's and preempts the worker CPUs. The worker CPUs in
turn preempt the central CPU when it needs tasks to run.

Currently, every CPU depends on its own tick to expire the current task. A
follow-up patch implementing tickless support for sched_ext will allow the
worker CPUs to go full tickless so that they can run completely undisturbed.

v3: - Kumar fixed a bug where the dispatch path could overflow the dispatch
      buffer if too many are dispatched to the fallback DSQ.

    - Use the new SCX_KICK_IDLE to wake up non-central CPUs.

    - Dropped '-p' option.

v2: - Use RESIZABLE_ARRAY() instead of fixed MAX_CPUS and use SCX_BUG[_ON]()
      to simplify error handling.

Signed-off-by: Tejun Heo 
Reviewed-by: David Vernet 
Acked-by: Josh Don 
Acked-by: Hao Luo 
Acked-by: Barret Rhoden 
Cc: Kumar Kartikeya Dwivedi 
Cc: Julia Lawall

sched_ext: Add scx_simple and scx_example_qmap example schedulers

2024-06-18T20:09:17+00:00

Add two simple example BPF schedulers - simple and qmap.

* simple: In terms of scheduling, it behaves identical to not having any
  operation implemented at all. The two operations it implements are only to
  improve visibility and exit handling. On certain homogeneous
  configurations, this actually can perform pretty well.

* qmap: A fixed five level priority scheduler to demonstrate queueing PIDs
  on BPF maps for scheduling. While not very practical, this is useful as a
  simple example and will be used to demonstrate different features.

v7: - Compat helpers stripped out in prepartion of upstreaming as the
      upstreamed patchset will be the baselinfe. Utility macros that can be
      used to implement compat features are kept.

    - Explicitly disable map autoattach on struct_ops to avoid trying to
      attach twice while maintaining compatbility with older libbpf.

v6: - Common header files reorganized and cleaned up. Compat helpers are
      added to demonstrate how schedulers can maintain backward
      compatibility with older kernels while making use of newly added
      features.

    - simple_select_cpu() added to keep track of the number of local
      dispatches. This is needed because the default ops.select_cpu()
      implementation is updated to dispatch directly and won't call
      ops.enqueue().

    - Updated to reflect the sched_ext API changes. Switching all tasks is
      the default behavior now and scx_qmap supports partial switching when
      `-p` is specified.

    - tools/sched_ext/Kconfig dropped. This will be included in the doc
      instead.

v5: - Improve Makefile. Build artifects are now collected into a separate
      dir which change be changed. Install and help targets are added and
      clean actually cleans everything.

    - MEMBER_VPTR() improved to improve access to structs. ARRAY_ELEM_PTR()
      and RESIZEABLE_ARRAY() are added to support resizable arrays in .bss.

    - Add scx_common.h which provides common utilities to user code such as
      SCX_BUG[_ON]() and RESIZE_ARRAY().

    - Use SCX_BUG[_ON]() to simplify error handling.

v4: - Dropped _example prefix from scheduler names.

v3: - Rename scx_example_dummy to scx_example_simple and restructure a bit
      to ease later additions. Comment updates.

    - Added declarations for BPF inline iterators. In the future, hopefully,
      these will be consolidated into a generic BPF header so that they
      don't need to be replicated here.

v2: - Updated with the generic BPF cpumask helpers.

Signed-off-by: Tejun Heo 
Reviewed-by: David Vernet 
Acked-by: Josh Don 
Acked-by: Hao Luo 
Acked-by: Barret Rhoden