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23b2b5ccc4
linux/kernel
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Chen Yu 23b2b5ccc4 sched/cache: Introduce helper functions to enforce LLC migration policy 
Cache-aware scheduling aggregates threads onto their preferred LLC,
mainly through load balancing. When the preferred LLC becomes
saturated, more threads are still placed there, increasing latency.
A mechanism is needed to limit aggregation so that the preferred LLC
does not become overloaded.

Introduce helper functions can_migrate_llc() and
can_migrate_llc_task() to enforce the LLC migration policy:

  1. Aggregate a task to its preferred LLC if both source and
     destination LLCs are not too busy, or if doing so will not
     leave the preferred LLC much more imbalanced than the
     non-preferred one (>20% utilization difference, a little
     higher than the default imbalance_pct(17%) of the LLC domain
     as hysteresis). Later this threshold will be turned into tunable
     debugfs.
  2. Allow moving a task from overloaded preferred LLC to a non
     preferred LLC if this will not cause the non preferred LLC
     to become too imbalanced to cause a later migration back.
  3. If both LLCs are too busy, let the generic load balance to
     spread the tasks.

Further (hysteresis)action could be taken in the future to prevent tasks
from being migrated into and out of the preferred LLC frequently (back and
forth): the threshold for migrating a task out of its preferred LLC should
be higher than that for migrating it into the LLC.

Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/d19b52589cdceaee5e625980959f4d1982d6d7c9.1775065312.git.tim.c.chen@linux.intel.com
2026-04-09 15:49:48 +02:00
..
bpf bpf: Fix sync_linked_regs regarding BPF_ADD_CONST32 zext propagation 2026-03-21 13:19:40 -07:00
cgroup cgroup: Don't expose dead tasks in cgroup 2026-03-06 12:43:25 -10:00
configs Remove WARN_ALL_UNSEEDED_RANDOM kernel config option 2026-02-23 11:18:48 -08:00
debug treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
dma dma-direct: prevent SWIOTLB path when DMA_ATTR_REQUIRE_COHERENT is set 2026-03-20 12:05:56 +01:00
entry Merge branch 'core/entry' into sched/core 2026-01-30 15:40:05 +01:00
events perf: Make sure to use pmu_ctx->pmu for groups 2026-03-12 11:29:16 +01:00
futex futex: Clear stale exiting pointer in futex_lock_pi() retry path 2026-03-28 13:54:02 +01:00
gcov Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
irq Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kcsan kcsan: test: Adjust "expect" allocation type for kmalloc_obj 2026-02-26 09:54:08 -08:00
livepatch Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
liveupdate liveupdate: luo_file: remember retrieve() status 2026-02-24 11:13:26 -08:00
locking sched/locking: Add special p->blocked_on==PROXY_WAKING value for proxy return-migration 2026-04-03 14:23:40 +02:00
module module: Fix kernel panic when a symbol st_shndx is out of bounds 2026-02-23 19:37:28 +00:00
power PM: sleep: Drop spurious WARN_ON() from pm_restore_gfp_mask() 2026-03-23 13:54:53 +01:00
printk Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
rcu srcu: Use irq_work to start GP in tiny SRCU 2026-03-25 09:00:05 -07:00
sched sched/cache: Introduce helper functions to enforce LLC migration policy 2026-04-09 15:49:48 +02:00
time alarmtimer: Fix argument order in alarm_timer_forward() 2026-03-24 23:17:14 +01:00
trace tracing: Drain deferred trigger frees if kthread creation fails 2026-03-28 08:32:44 -04:00
unwind Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
.gitignore
acct.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
async.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
audit_fsnotify.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
audit_tree.c Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
audit_watch.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
audit.c Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
audit.h audit: fix comment misindentation in audit.h 2025-10-22 19:28:06 -04:00
auditfilter.c Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
auditsc.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
backtracetest.c
bounds.c x86/asm: Remove ANNOTATE_DATA_SPECIAL usage 2025-12-03 16:53:19 +01:00
capability.c
cfi.c
compat.c
configs.c
context_tracking.c context_tracking: Remove rcu_task_trace_heavyweight_{enter,exit}() 2026-01-01 16:39:46 +08:00
cpu_pm.c syscore: Pass context data to callbacks 2025-11-14 10:01:52 +01:00
cpu.c SPDX updates for 7.0-rc1 2026-02-17 09:46:03 -08:00
crash_core_test.c
crash_core.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
crash_dump_dm_crypt.c crash_dump: don't log dm-crypt key bytes in read_key_from_user_keying 2026-03-10 16:01:48 -07:00
crash_reserve.c crash: let architecture decide crash memory export to iomem_resource 2025-11-12 10:00:15 -08:00
cred.c cred: remove unused set_security_override_from_ctx() 2026-01-06 20:52:57 -05:00
delayacct.c delayacct: fix uapi timespec64 definition 2026-02-08 00:13:32 -08:00
dma.c
elfcorehdr.c
exec_domain.c
exit.c kthread: consolidate kthread exit paths to prevent use-after-free 2026-02-26 10:45:49 +01:00
exit.h
extable.c
fail_function.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
fork.c sched/cache: Introduce infrastructure for cache-aware load balancing 2026-04-09 15:49:47 +02:00
freezer.c freezer: Clarify that only cgroup1 freezer uses PM freezer 2025-10-30 20:10:27 +01:00
gen_kheaders.sh
groups.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
hung_task.c hung_task: add hung_task_sys_info sysctl to dump sys info on task-hung 2025-11-20 14:03:43 -08:00
iomem.c
irq_work.c
jump_label.c
kallsyms_internal.h kallsyms: Get rid of kallsyms relative base 2026-01-22 15:58:22 -07:00
kallsyms_selftest.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kallsyms_selftest.h
kallsyms.c mm.git review status for linus..mm-nonmm-stable 2026-02-12 12:13:01 -08:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.kexec liveupdate: kho: move to kernel/liveupdate 2025-11-27 14:24:33 -08:00
Kconfig.locks
Kconfig.preempt sched: Further restrict the preemption modes 2026-01-08 12:43:57 +01:00
kcov.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kexec_core.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kexec_elf.c
kexec_file.c kexec: derive purgatory entry from symbol 2026-01-31 16:16:07 -08:00
kexec_internal.h
kexec.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kheaders.c
kprobes.c kprobes: Remove unneeded warnings from __arm_kprobe_ftrace() 2026-03-13 23:15:26 +09:00
kstack_erase.c sysctl: remove __user qualifier from stack_erasing_sysctl buffer argument 2025-11-27 15:44:53 +01:00
ksyms_common.c
ksysfs.c kexec: move sysfs entries to /sys/kernel/kexec 2025-11-27 14:24:42 -08:00
kthread.c kthread: consolidate kthread exit paths to prevent use-after-free 2026-02-26 10:45:49 +01:00
latencytop.c
Makefile kcov: Enable context analysis 2026-01-05 16:43:34 +01:00
module_signature.c
notifier.c
nscommon.c nsfs: tighten permission checks for ns iteration ioctls 2026-02-27 22:00:08 +01:00
nsproxy.c nsproxy: fix free_nsproxy() and simplify create_new_namespaces() 2025-11-14 13:10:38 +01:00
nstree.c nstree: tighten permission checks for listing 2026-02-27 22:00:11 +01:00
padata.c Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
panic.c panic: add panic_force_cpu= parameter to redirect panic to a specific CPU 2026-02-03 08:21:26 -08:00
params.c Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
pid_namespace.c pid: rely on common reference count behavior 2025-11-11 10:01:32 +01:00
pid_sysctl.h
pid.c Revert "pid: make __task_pid_nr_ns(ns => NULL) safe for zombie callers" 2026-02-10 11:39:30 +01:00
profile.c
ptrace.c rseq: Introduce struct rseq_data 2025-11-04 08:30:50 +01:00
range.c
reboot.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
regset.c
relay.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
resource_kunit.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
resource.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
rseq.c rseq: slice ext: Ensure rseq feature size differs from original rseq size 2026-02-23 11:19:19 +01:00
scftorture.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
scs.c scs: fix a wrong parameter in __scs_magic 2025-11-12 10:00:13 -08:00
seccomp.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
signal.c compiler-context-analysis: Remove __cond_lock() function-like helper 2026-01-05 16:43:33 +01:00
smp.c smp: Introduce a helper function to check for pending IPIs 2025-11-19 18:06:50 +01:00
smpboot.c
smpboot.h
softirq.c
stacktrace.c
static_call_inline.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
static_call.c
stop_machine.c
sys_ni.c rseq: Implement sys_rseq_slice_yield() 2026-01-22 11:11:17 +01:00
sys.c RISC-V updates for v7.0 2026-02-12 19:17:44 -08:00
sysctl-test.c
sysctl.c sysctl: fix uninitialized variable in proc_do_large_bitmap 2026-03-26 09:32:19 +01:00
task_work.c task_work: Fix NMI race condition 2025-10-29 10:29:54 +01:00
taskstats.c
torture.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
tracepoint.c Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
tsacct.c tsacct: skip all kernel threads 2026-01-26 19:07:13 -08:00
ucount.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
uid16.c
uid16.h
umh.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
up.c
user_namespace.c Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
user-return-notifier.c
user.c ns: drop custom reference count initialization for initial namespaces 2025-11-11 10:01:32 +01:00
utsname_sysctl.c
utsname.c namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
vhost_task.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
vmcore_info.c mm.git review status for linus..mm-nonmm-stable 2026-02-12 12:13:01 -08:00
watch_queue.c Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
watchdog_buddy.c
watchdog_perf.c watchdog/hardlockup: simplify perf event probe and remove per-cpu dependency 2026-02-08 00:13:35 -08:00
watchdog.c watchdog/softlockup: fix sample ring index wrap in need_counting_irqs() 2026-02-08 00:13:34 -08:00
workqueue_internal.h workqueue: Show in-flight work item duration in stall diagnostics 2026-03-05 07:27:48 -10:00
workqueue.c workqueue: Rename show_cpu_pool{s,}_hog{s,}() to reflect broadened scope 2026-03-06 06:38:16 -10:00