mirror of https://github.com/torvalds/linux.git
1d6d399223
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.
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Merge tag 'kthread-for-6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks
Pull kthread updates from Frederic Weisbecker:
"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"
* tag 'kthread-for-6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks:
kthread: modify kernel-doc function name to match code
rcu: Use kthread preferred affinity for RCU exp kworkers
treewide: Introduce kthread_run_worker[_on_cpu]()
kthread: Unify kthread_create_on_cpu() and kthread_create_worker_on_cpu() automatic format
rcu: Use kthread preferred affinity for RCU boost
kthread: Implement preferred affinity
mm: Create/affine kswapd to its preferred node
mm: Create/affine kcompactd to its preferred node
kthread: Default affine kthread to its preferred NUMA node
kthread: Make sure kthread hasn't started while binding it
sched,arm64: Handle CPU isolation on last resort fallback rq selection
arm64: Exclude nohz_full CPUs from 32bits el0 support
lib: test_objpool: Use kthread_run_on_cpu()
kallsyms: Use kthread_run_on_cpu()
soc/qman: test: Use kthread_run_on_cpu()
arm/bL_switcher: Use kthread_run_on_cpu()
|
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|---|---|---|
| .. | ||
| asymmetric_keys | ||
| async_tx | ||
| 842.c | ||
| Kconfig | ||
| Makefile | ||
| acompress.c | ||
| adiantum.c | ||
| aead.c | ||
| aegis-neon.h | ||
| aegis.h | ||
| aegis128-core.c | ||
| aegis128-neon-inner.c | ||
| aegis128-neon.c | ||
| aes_generic.c | ||
| aes_ti.c | ||
| af_alg.c | ||
| ahash.c | ||
| akcipher.c | ||
| algapi.c | ||
| algboss.c | ||
| algif_aead.c | ||
| algif_hash.c | ||
| algif_rng.c | ||
| algif_skcipher.c | ||
| ansi_cprng.c | ||
| anubis.c | ||
| api.c | ||
| arc4.c | ||
| aria_generic.c | ||
| authenc.c | ||
| authencesn.c | ||
| blake2b_generic.c | ||
| blowfish_common.c | ||
| blowfish_generic.c | ||
| bpf_crypto_skcipher.c | ||
| camellia_generic.c | ||
| cast5_generic.c | ||
| cast6_generic.c | ||
| cast_common.c | ||
| cbc.c | ||
| ccm.c | ||
| chacha20poly1305.c | ||
| chacha_generic.c | ||
| cipher.c | ||
| cmac.c | ||
| compress.c | ||
| compress.h | ||
| crc32_generic.c | ||
| crc32c_generic.c | ||
| crc64_rocksoft_generic.c | ||
| crct10dif_common.c | ||
| crct10dif_generic.c | ||
| cryptd.c | ||
| crypto_engine.c | ||
| crypto_null.c | ||
| crypto_user.c | ||
| ctr.c | ||
| cts.c | ||
| curve25519-generic.c | ||
| deflate.c | ||
| des_generic.c | ||
| dh.c | ||
| dh_helper.c | ||
| drbg.c | ||
| ecb.c | ||
| ecc.c | ||
| ecc_curve_defs.h | ||
| ecdh.c | ||
| ecdh_helper.c | ||
| ecdsa-p1363.c | ||
| ecdsa-x962.c | ||
| ecdsa.c | ||
| ecdsasignature.asn1 | ||
| echainiv.c | ||
| ecrdsa.c | ||
| ecrdsa_defs.h | ||
| ecrdsa_params.asn1 | ||
| ecrdsa_pub_key.asn1 | ||
| essiv.c | ||
| fcrypt.c | ||
| fips.c | ||
| gcm.c | ||
| geniv.c | ||
| ghash-generic.c | ||
| hash.h | ||
| hash_info.c | ||
| hctr2.c | ||
| hmac.c | ||
| internal.h | ||
| jitterentropy-kcapi.c | ||
| jitterentropy-testing.c | ||
| jitterentropy.c | ||
| jitterentropy.h | ||
| kdf_sp800108.c | ||
| keywrap.c | ||
| khazad.c | ||
| kpp.c | ||
| lrw.c | ||
| lskcipher.c | ||
| lz4.c | ||
| lz4hc.c | ||
| lzo-rle.c | ||
| lzo.c | ||
| md4.c | ||
| md5.c | ||
| michael_mic.c | ||
| nhpoly1305.c | ||
| pcbc.c | ||
| pcrypt.c | ||
| poly1305_generic.c | ||
| polyval-generic.c | ||
| proc.c | ||
| ripemd.h | ||
| rmd160.c | ||
| rng.c | ||
| rsa-pkcs1pad.c | ||
| rsa.c | ||
| rsa_helper.c | ||
| rsaprivkey.asn1 | ||
| rsapubkey.asn1 | ||
| rsassa-pkcs1.c | ||
| scatterwalk.c | ||
| scompress.c | ||
| seed.c | ||
| seqiv.c | ||
| serpent_generic.c | ||
| sha1_generic.c | ||
| sha3_generic.c | ||
| sha256_generic.c | ||
| sha512_generic.c | ||
| shash.c | ||
| sig.c | ||
| simd.c | ||
| skcipher.c | ||
| skcipher.h | ||
| sm3.c | ||
| sm3_generic.c | ||
| sm4.c | ||
| sm4_generic.c | ||
| streebog_generic.c | ||
| tcrypt.c | ||
| tcrypt.h | ||
| tea.c | ||
| testmgr.c | ||
| testmgr.h | ||
| twofish_common.c | ||
| twofish_generic.c | ||
| vmac.c | ||
| wp512.c | ||
| xcbc.c | ||
| xctr.c | ||
| xor.c | ||
| xts.c | ||
| xxhash_generic.c | ||
| zstd.c | ||