| Message ID | Z42M-Zqd3kBNCfgz@pavilion.home (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [GIT,PULL] kthread updates for v6.14 | expand |
The pull request you sent on Mon, 20 Jan 2025 00:38:33 +0100:
> git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git tags/kthread-for-6.14-rc1
has been merged into torvalds/linux.git:
https://git.kernel.org/torvalds/c/1d6d3992235ed08929846f98fecf79682e0b422c
Thank you!
Hi Linus, A pull request from me on the topic of kthreads may appear out of the blue but this "subsystem" has no official maintainer and nobody loudly volunteered to take these changes. Therefore I'm carrying these myself. Thanks. The following changes since commit fac04efc5c793dccbd07e2d59af9f90b7fc0dca4: Linux 6.13-rc2 (2024-12-08 14:03:39 -0800) are available in the Git repository at: git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git tags/kthread-for-6.14-rc1 for you to fetch changes up to d8b4bf4ea04dd96fe43f6010c614149aba4c9b91: kthread: modify kernel-doc function name to match code (2025-01-13 11:33:26 +0100) ---------------------------------------------------------------- Kthreads affinity follow either of 4 existing different patterns: 1) Per-CPU kthreads must stay affine to a single CPU and never execute relevant code on any other CPU. This is currently handled by smpboot code which takes care of CPU-hotplug operations. Affinity here is a correctness constraint. 2) Some kthreads _have_ to be affine to a specific set of CPUs and can't run anywhere else. The affinity is set through kthread_bind_mask() and the subsystem takes care by itself to handle CPU-hotplug operations. Affinity here is assumed to be a correctness constraint. 3) Per-node kthreads _prefer_ to be affine to a specific NUMA node. This is not a correctness constraint but merely a preference in terms of memory locality. kswapd and kcompactd both fall into this category. The affinity is set manually like for any other task and CPU-hotplug is supposed to be handled by the relevant subsystem so that the task is properly reaffined whenever a given CPU from the node comes up. Also care should be taken so that the node affinity doesn't cross isolated (nohz_full) cpumask boundaries. 4) Similar to the previous point except kthreads have a _preferred_ affinity different than a node. Both RCU boost kthreads and RCU exp kworkers fall into this category as they refer to "RCU nodes" from a distinctly distributed tree. Currently the preferred affinity patterns (3 and 4) have at least 4 identified users, with more or less success when it comes to handle CPU-hotplug operations and CPU isolation. Each of which do it in its own ad-hoc way. This is an infrastructure proposal to handle this with the following API changes: _ kthread_create_on_node() automatically affines the created kthread to its target node unless it has been set as per-cpu or bound with kthread_bind[_mask]() before the first wake-up. - kthread_affine_preferred() is a new function that can be called right after kthread_create_on_node() to specify a preferred affinity different than the specified node. When the preferred affinity can't be applied because the possible targets are offline or isolated (nohz_full), the kthread is affine to the housekeeping CPUs (which means to all online CPUs most of the time or only the non-nohz_full CPUs when nohz_full= is set). kswapd, kcompactd, RCU boost kthreads and RCU exp kworkers have been converted, along with a few old drivers. Summary of the changes: * Consolidate a bunch of ad-hoc implementations of kthread_run_on_cpu() * Introduce task_cpu_fallback_mask() that defines the default last resort affinity of a task to become nohz_full aware * Add some correctness check to ensure kthread_bind() is always called before the first kthread wake up. * Default affine kthread to its preferred node. * Convert kswapd / kcompactd and remove their halfway working ad-hoc affinity implementation * Implement kthreads preferred affinity * Unify kthread worker and kthread API's style * Convert RCU kthreads to the new API and remove the ad-hoc affinity implementation. ---------------------------------------------------------------- Frederic Weisbecker (15): arm/bL_switcher: Use kthread_run_on_cpu() soc/qman: test: Use kthread_run_on_cpu() kallsyms: Use kthread_run_on_cpu() lib: test_objpool: Use kthread_run_on_cpu() arm64: Exclude nohz_full CPUs from 32bits el0 support sched,arm64: Handle CPU isolation on last resort fallback rq selection kthread: Make sure kthread hasn't started while binding it kthread: Default affine kthread to its preferred NUMA node mm: Create/affine kcompactd to its preferred node mm: Create/affine kswapd to its preferred node kthread: Implement preferred affinity rcu: Use kthread preferred affinity for RCU boost kthread: Unify kthread_create_on_cpu() and kthread_create_worker_on_cpu() automatic format treewide: Introduce kthread_run_worker[_on_cpu]() rcu: Use kthread preferred affinity for RCU exp kworkers Randy Dunlap (1): kthread: modify kernel-doc function name to match code Documentation/arch/arm64/asymmetric-32bit.rst | 8 + arch/arm/common/bL_switcher.c | 10 +- arch/arm64/include/asm/cpufeature.h | 1 + arch/arm64/include/asm/mmu_context.h | 14 +- arch/arm64/kernel/cpufeature.c | 15 +- arch/x86/kvm/i8254.c | 2 +- crypto/crypto_engine.c | 2 +- drivers/cpufreq/cppc_cpufreq.c | 2 +- drivers/gpu/drm/drm_vblank_work.c | 2 +- .../gpu/drm/i915/gem/selftests/i915_gem_context.c | 2 +- drivers/gpu/drm/i915/gt/selftest_execlists.c | 2 +- drivers/gpu/drm/i915/gt/selftest_hangcheck.c | 2 +- drivers/gpu/drm/i915/gt/selftest_slpc.c | 2 +- drivers/gpu/drm/i915/selftests/i915_request.c | 8 +- drivers/gpu/drm/msm/disp/msm_disp_snapshot.c | 2 +- drivers/gpu/drm/msm/msm_atomic.c | 2 +- drivers/gpu/drm/msm/msm_gpu.c | 2 +- drivers/gpu/drm/msm/msm_kms.c | 2 +- .../media/platform/chips-media/wave5/wave5-vpu.c | 2 +- drivers/net/dsa/mv88e6xxx/chip.c | 2 +- drivers/net/ethernet/intel/ice/ice_dpll.c | 2 +- drivers/net/ethernet/intel/ice/ice_gnss.c | 2 +- drivers/net/ethernet/intel/ice/ice_ptp.c | 2 +- drivers/platform/chrome/cros_ec_spi.c | 2 +- drivers/ptp/ptp_clock.c | 2 +- drivers/soc/fsl/qbman/qman_test_stash.c | 6 +- drivers/spi/spi.c | 2 +- drivers/usb/typec/tcpm/tcpm.c | 2 +- drivers/vdpa/vdpa_sim/vdpa_sim.c | 2 +- drivers/watchdog/watchdog_dev.c | 2 +- fs/erofs/zdata.c | 2 +- include/linux/cpuhotplug.h | 1 + include/linux/kthread.h | 56 +++++- include/linux/mmu_context.h | 1 + kernel/kallsyms_selftest.c | 4 +- kernel/kthread.c | 203 ++++++++++++++++++--- kernel/rcu/tree.c | 94 ++-------- kernel/rcu/tree_plugin.h | 11 +- kernel/sched/core.c | 2 +- kernel/sched/ext.c | 2 +- kernel/workqueue.c | 2 +- lib/test_objpool.c | 19 +- mm/compaction.c | 43 +---- mm/vmscan.c | 8 +- net/dsa/tag_ksz.c | 2 +- net/dsa/tag_ocelot_8021q.c | 2 +- net/dsa/tag_sja1105.c | 2 +- 47 files changed, 341 insertions(+), 221 deletions(-)