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fcceb7da94
linux/kernel
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Jemmy Wong fcceb7da94 sched/cache: Avoid publishing partial LLC utilization 
update_sg_lb_stats() sums utilization over the CPUs in both
sched_group_span(group) and env->cpus, but takes capacity from
group->sgc->capacity for the whole group. record_sg_llc_stats()
publishes both.

Rejecting an all-affinity-pinned source runqueue removes that CPU from
env->cpus and retries group selection. The retry can publish the
partial utilization with the full capacity.

can_migrate_llc() then treats a busy preferred LLC as having spare
capacity. More tasks can aggregate into it, migrations out can be
blocked, and two busy LLCs may not fall back to generic balancing.
This increases CPU contention and task latency. Found by inspection.

Skip publication on affinity retries using LBF_ALL_PINNED, retaining
the first-pass snapshots and avoiding repeated cpumask checks. On the
first pass, publish either shared LLC statistic only when env->cpus
covers the whole group. Load balancing still uses the affinity-filtered
statistics.

The same window exists during CPU hotplug. env->cpus drops a CPU at
set_cpu_active(false), but the group span and sgc->capacity still
include it until cpuset_cpu_inactive() rebuilds the domains. Keeping
the previous snapshot avoids the mismatched publish. After the rebuild,
the next periodic balance records both statistics again.

Fixes: f025ef2753 ("sched/cache: Record per LLC utilization to guide cache aware scheduling decisions")
Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Suggested-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Jemmy Wong <jemmywong512@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20261013084338.55100-1-jemmywong512@gmail.com
2026-10-16 09:49:04 +02:00
..
bpf bpf-fixes 2026-09-06 13:49:44 -07:00
cgroup cgroup: Fixes for v7.3-rc3 2026-09-15 11:40:30 -07:00
configs slab: support for compiler-assisted type-based slab cache partitioning 2026-05-14 10:44:09 +02:00
debug kgdb: update outdated references to kgdb_wait() 2026-04-21 16:41:54 +01:00
dma dma-mapping fixes for Linux 7.3 2026-09-17 08:03:37 -07:00
entry Merge branch 'tip/sched/urgent' 2026-10-13 13:51:24 +02:00
events perf: Fix null pointer access in is_include_guest_event() 2026-09-18 12:19:43 +02:00
futex Misc locking fixes: 2026-09-06 10:45:46 -07:00
gcov Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
irq treewide: refresh kmalloc_obj() conversions 2026-09-04 21:37:00 -07:00
kcsan kcsan: avoid unintended access checking in NMIs 2026-07-20 18:18:37 +02:00
livepatch livepatch: Fix NULL pointer dereference in klp_find_func() 2026-07-07 12:54:37 +02:00
liveupdate kho: make boot time huge page allocation work nicely with KHO 2026-08-23 09:17:38 -07:00
locking Misc locking fixes: 2026-09-06 10:45:46 -07:00
module module: validate string table section types 2026-08-06 16:44:45 +02:00
power PM: sleep: Allow disabling DPM watchdog by default 2026-07-23 15:46:34 +02:00
printk Merge branch 'for-7.4-trivial' into for-linus 2026-09-09 09:52:21 +02:00
rcu RCU updates: 2026-08-23 18:00:22 -07:00
sched sched/cache: Avoid publishing partial LLC utilization 2026-10-16 09:49:04 +02:00
time sched/cputime: Don't account idle time twice after dyntick-idle 2026-10-16 09:49:03 +02:00
trace ring-buffer: Check resize_disabled before publishing the new subbuf order 2026-09-13 13:06:43 -04:00
unwind Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
.gitignore
acct.c fs: move SB_I_USERNS_VISIBLE to FS_USERNS_MOUNT_RESTRICTED 2026-05-11 23:13:01 +02:00
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 audit: fix recursive locking deadlock in audit_dupe_exe() 2026-05-27 19:15:34 -04:00
audit_tree.c audit: use 'unsigned int' instead of 'unsigned' 2026-05-26 17:15:30 -04:00
audit_watch.c audit: drop BUG_ON() from audit_add_to_parent() 2026-07-28 15:53:48 -04:00
audit.c audit: fix potential integer overflow in audit_log_n_string() 2026-07-29 16:19:06 -04:00
audit.h audit: fix recursive locking deadlock in audit_dupe_exe() 2026-05-27 19:15:34 -04:00
auditfilter.c audit/stable-7.3 PR 20260814 2026-08-19 16:21:32 -07:00
auditsc.c audit: drop BUG_ON() from audit_signal_info_syscall() 2026-07-28 15:53:49 -04:00
backtracetest.c
bounds.c
capability.c capability: unexport has_capability_noaudit 2026-08-21 09:09:55 +02:00
cfi.c
compat.c
configs.c
context_tracking.c
cpu_pm.c
cpu.c cpumask: Introduce cpu_preferred_mask 2026-09-28 08:44:41 +02:00
crash_core_test.c
crash_core.c powerpc/kexec_file: Use crash_exclude_core_ranges() helper 2026-06-30 18:49:06 +03:00
crash_dump_dm_crypt.c crash_dump: release keyring reference at the correct time 2026-07-13 10:04:47 +03:00
crash_reserve.c kernel/crash: remove inclusion of crypto/sha1.h 2026-03-27 21:19:46 -07:00
cred.c exec_state: relocate dumpable information 2026-05-26 11:02:01 +02:00
delayacct.c sysctl: remove CONFIG_PROC_SYSCTL, it just mirrors CONFIG_SYSCTL 2026-08-05 15:28:23 +02:00
dma.c
elfcorehdr.c
exec_domain.c
exec_state.c exec_state: relocate dumpable information 2026-05-26 11:02:01 +02:00
exit.c sched/cache: Introduce task_struct->sched_cache_grp to fix UAF 2026-09-22 10:50:43 +02:00
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 task_struct->sched_cache_grp to fix UAF 2026-09-22 10:50:43 +02:00
freezer.c
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: explicitly report I/O wait state in log output 2026-03-27 21:19:40 -07:00
iomem.c
irq_work.c irq_work: Flush lazy work CPU down on PREEMPT_RT 2026-10-01 14:00:35 +02:00
jump_label.c treewide: refresh kmalloc_obj() conversions 2026-09-04 21:37:00 -07:00
kallsyms_internal.h
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
kcmp.c fs: add real_fs to track task's actual fs_struct 2026-06-29 10:43:45 +02:00
Kconfig.freezer
Kconfig.hz
Kconfig.kexec
Kconfig.locks locking/qspinlock: Add contended_release tracepoint 2026-08-07 17:58:10 +02:00
Kconfig.preempt cpumask: Introduce cpu_preferred_mask 2026-09-28 08:44:41 +02:00
kcov.c mm.git review status for master..mm-nonmm-stable 2026-08-23 08:07:11 -07:00
kexec_core.c liveupdate: skip serialization for context-preserving kexec 2026-06-01 09:19:38 +03:00
kexec_elf.c
kexec_file.c kexec_file: skip checksum verification when safe 2026-07-01 13:01:08 +03:00
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: Protect kprobe_blacklist with RCU 2026-09-03 09:04:25 +09:00
kstack_erase.c
ksyms_common.c
ksysfs.c kernel: ksysfs: initialize kernel_kobj earlier 2026-04-03 19:39:52 +02:00
kthread.c treewide: refresh kmalloc_obj() conversions 2026-09-04 21:37:00 -07:00
latencytop.c
Makefile exec: introduce struct task_exec_state 2026-05-26 11:02:01 +02:00
module_signature.c module: Give 'enum pkey_id_type' a more specific name 2026-03-24 21:42:37 +00:00
notifier.c
nscommon.c nsfs: tighten permission checks for ns iteration ioctls 2026-02-27 22:00:08 +01:00
nsproxy.c vfs-7.1-rc1.mount.v2 2026-04-14 19:59:25 -07:00
nstree.c nstree: check listing permission before taking a namespace reference 2026-09-09 10:03:15 +02:00
padata.c padata: Put CPU offline callback in ONLINE section to allow failure 2026-03-22 11:17:59 +09:00
panic.c bug/kunit: Core support for suppressing warning backtraces 2026-05-14 10:50:00 -06:00
params.c mm.git review status for master..mm-nonmm-stable 2026-08-23 08:07:11 -07:00
pid_namespace.c pid_namespace: allow opening pid_for_children before init was created 2026-03-20 14:44:26 +01:00
pid_sysctl.h
pid.c Summary 2026-08-20 08:46:41 -07:00
profile.c
ptrace.c exec_state: relocate dumpable information 2026-05-26 11:02:01 +02:00
range.c
reboot.c reboot: fix cad_pid use-after-free race 2026-08-31 10:25:46 +02:00
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 resource: downgrade "resource sanity check" warning to debug level 2026-08-03 21:10:05 -07:00
rseq.c rseq: Reenable performance optimizations conditionally 2026-05-06 17:40:27 +02:00
scftorture.c smp_call_function() torture-test updates: 2026-08-23 19:28:04 -07:00
scs.c
seccomp.c seccomp, treewide: Rename and convert __secure_computing() to return boolean 2026-07-12 12:38:02 +02:00
signal.c signal: Prevent exec() race 2026-09-16 18:44:03 +02:00
smp.c irq_work: Flush lazy work CPU down on PREEMPT_RT 2026-10-01 14:00:35 +02:00
smpboot.c smpboot: Don't park the thread if work is pending 2026-10-01 14:00:36 +02:00
smpboot.h
softirq.c interrupt: Disable interrupt before modifying hardirq_disable counter 2026-08-30 08:39:04 +02:00
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 stop_machine: Make stop_one_cpu_nowait() return void 2026-07-31 12:35:26 +02:00
sys_ni.c time: Respect COMPAT_32BIT_TIME for old time type functions 2026-07-07 23:52:53 +02:00
sys.c prctl: fix PR_SET_MM_AUXV losing the forced AT_NULL terminator 2026-08-19 19:55:05 -07:00
sysctl-test.c
sysctl.c sysctl: remove CONFIG_PROC_SYSCTL, it just mirrors CONFIG_SYSCTL 2026-08-05 15:28:23 +02:00
task_work.c
taskstats.c taskstats: fold the two cpumask handlers into one 2026-08-13 15:42:05 -07:00
torture.c torture: Don't leak shuffle_tmp_mask when shuffler kthread fails to start 2026-08-14 14:59:21 -07:00
tracepoint.c tracepoint: balance regfunc() on func_add() failure in tracepoint_add_func() 2026-04-14 05:17:02 -04:00
tsacct.c
ucount.c binfmt_misc: correctly account pre-opened interpreters 2026-08-03 23:36:18 +02:00
uid16.c
uid16.h
umh.c fs: add umh argument to struct kernel_clone_args 2026-06-29 10:54:41 +02:00
up.c smp: Refactor remote CPU selection in smp_call_function_any() 2026-07-16 09:24:55 +02:00
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 binfmt_misc: use RCU for the handler lookup 2026-08-03 10:08:36 +02:00
utsname_sysctl.c sysctl: remove CONFIG_PROC_SYSCTL, it just mirrors CONFIG_SYSCTL 2026-08-05 15:28:23 +02:00
utsname.c
vhost_task.c vhost_task_create: kill unnecessary .exit_signal initialization 2026-06-10 02:17:00 -04:00
vmcore_info.c mm.git review status for linus..mm-nonmm-stable 2026-04-16 20:11:56 -07:00
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/hardlockup: improve buddy system detection timeliness 2026-03-27 21:19:47 -07:00
watchdog_perf.c
watchdog.c watchdog/softlockup: fix softlockup typos 2026-08-03 21:10:06 -07:00
workqueue_internal.h workqueue: Show in-flight work item duration in stall diagnostics 2026-03-05 07:27:48 -10:00
workqueue.c workqueue: Fixes for v7.3-rc1 2026-08-31 14:38:40 -07:00