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Jan H. Schönherr eebe6446cc perf/core: Speed up kexec shutdown by avoiding unnecessary cross CPU calls 
There are typically a lot of PMUs registered, but in many cases only few
of them have an event registered (like the "cpu" PMU in the presence of
the watchdog). As the mutex is already held, it's safe to just check for
existing events before doing the cross CPU call.

This change saves tens of milliseconds from kexec time (perceived as
steal time during a hypervisor host update), with <2ms remaining for
this step in the shutdown. There might be additional potential for
parallelization or we could just disable performance monitoring during
the actual shutdown and be less graceful about it.

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
 		2026-01-13 21:39:01 +01:00
..
bpf Some filesystems use a kinda-sorta controlled dentry refcount leak to pin 2025-12-05 14:36:21 -08:00
cgroup Significant patch series in this merge are as follows: 2025-12-05 13:52:43 -08:00
configs hung_task: panic when there are more than N hung tasks at the same time 2025-11-12 10:00:14 -08:00
debug kdb: Adapt kdb_msg_write to work with NBCON consoles 2025-10-24 12:56:20 +02:00
dma dma-mapping fixes for Linux 6.19: 2025-12-11 08:14:23 +09:00
entry rseq: Switch to TIF_RSEQ if supported 2025-11-04 08:35:37 +01:00
events perf/core: Speed up kexec shutdown by avoiding unnecessary cross CPU calls 2026-01-13 21:39:01 +01:00
futex Futex changes for v6.19: 2025-12-10 17:21:30 +09:00
gcov gcov: add support for GCC 15 2025-11-09 21:19:44 -08:00
irq Misc fixes: 2025-12-14 06:07:09 +12:00
kcsan Kernel Concurrency Sanitizer (KCSAN) updates for v6.18 2025-10-02 08:31:44 -07:00
livepatch livepatching changes for 6.19 2025-12-03 13:46:48 -08:00
liveupdate mm: memfd_luo: add CONFIG_SHMEM dependency 2025-12-10 16:07:44 -08:00
locking RCU pull request for v6.19 2025-12-03 12:18:07 -08:00
module Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
power Merge branches 'pm-qos' and 'pm-tools' 2025-11-28 16:50:45 +01:00
printk soc: driver updates for 6.19 2025-12-05 17:29:04 -08:00
rcu RCU pull request for v6.19 2025-12-03 12:18:07 -08:00
sched Miscellaneous scheduler fixes/cleanups: 2025-12-06 12:31:21 -08:00
time soc: driver updates for 6.19 2025-12-05 17:29:04 -08:00
trace tracing fixes for v6.19: 2025-12-06 13:49:40 -08:00
unwind unwind_user/fp: Use dummies instead of ifdef 2025-12-17 13:31:07 +01:00
.gitignore kheaders: rebuild kheaders_data.tar.xz when a file is modified within a minute 2025-06-24 20:30:37 +09:00
Kconfig.freezer
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Kconfig.hz kernel: Fix "select" wording on HZ_250 description 2025-02-21 09:20:30 +01:00
Kconfig.kexec liveupdate: kho: move to kernel/liveupdate 2025-11-27 14:24:33 -08:00
Kconfig.locks
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Kconfig.preempt softirq: Allow to drop the softirq-BKL lock on PREEMPT_RT 2025-09-17 16:25:41 +02:00
Makefile liveupdate: kho: move to kernel/liveupdate 2025-11-27 14:24:33 -08:00
acct.c act: use credential guards in acct_write_process() 2025-11-04 12:36:49 +01:00
async.c
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audit.c audit: fix skb leak when audit rate limit is exceeded 2025-09-10 19:55:00 -04:00
audit.h audit: fix comment misindentation in audit.h 2025-10-22 19:28:06 -04:00
audit_fsnotify.c VFS/audit: introduce kern_path_parent() for audit 2025-09-23 12:37:35 +02:00
audit_tree.c mount-related stuff for this cycle 2025-10-03 10:19:44 -07:00
audit_watch.c VFS/audit: introduce kern_path_parent() for audit 2025-09-23 12:37:35 +02:00
auditfilter.c audit: Use kzalloc() instead of kmalloc()/memset() in audit_krule_to_data() 2025-11-07 16:38:34 -05:00
auditsc.c audit: merge loops in __audit_inode_child() 2025-11-07 16:50:42 -05:00
backtracetest.c
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bounds.c x86/asm: Remove ANNOTATE_DATA_SPECIAL usage 2025-12-03 16:53:19 +01:00
capability.c capability: Remove unused has_capability 2025-03-07 22:03:09 -06:00
cfi.c cfi: Move BPF CFI types and helpers to generic code 2025-07-31 18:23:53 -07:00
compat.c
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configs.c
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context_tracking.c context_tracking: Make RCU watch ct_kernel_exit_state() warning 2025-03-04 18:44:29 -08:00
cpu.c cpu: Make atomic hotplug callbacks run with interrupts disabled on UP 2025-12-10 15:49:11 +09:00
cpu_pm.c syscore: Pass context data to callbacks 2025-11-14 10:01:52 +01:00
crash_core.c crash: fix crashkernel resource shrink 2025-11-15 10:52:01 -08:00
crash_core_test.c crash: add KUnit tests for crash_exclude_mem_range 2025-09-13 17:32:55 -07:00
crash_dump_dm_crypt.c crash_dump: retrieve dm crypt keys in kdump kernel 2025-05-21 10:48:21 -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 kernel-6.19-rc1.cred 2025-12-01 13:45:41 -08:00
delayacct.c delayacct: remove redundant code and adjust indentation 2025-05-27 19:40:33 -07:00
dma.c
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elfcorehdr.c
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exec_domain.c
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exit.c Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
exit.h
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extable.c
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fail_function.c
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fork.c Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
freezer.c freezer: Clarify that only cgroup1 freezer uses PM freezer 2025-10-30 20:10:27 +01:00
gen_kheaders.sh kheaders: make it possible to override TAR 2025-08-06 10:23:36 +09:00
groups.c
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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 mm/memremap: Pass down MEMREMAP_* flags to arch_memremap_wb() 2025-02-21 15:05:38 +01:00
irq_work.c kasan: make kasan_record_aux_stack_noalloc() the default behaviour 2025-01-13 22:40:36 -08:00
jump_label.c jump_label: Use RCU in all users of __module_text_address(). 2025-03-10 11:54:46 +01:00
kallsyms.c kallsyms: Fix wrong "big" kernel symbol type read from procfs 2025-11-24 16:56:24 +01:00
kallsyms_internal.h
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kallsyms_selftest.c kallsyms: use kmalloc_array() instead of kmalloc() 2025-09-28 11:36:14 -07:00
kallsyms_selftest.h
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kcmp.c kcmp: improve performance adding an unlikely hint to task comparisons 2025-02-21 10:25:33 +01:00
kcov.c kcov: use write memory barrier after memcpy() in kcov_move_area() 2025-09-13 17:32:44 -07:00
kexec.c kexec: enable CMA based contiguous allocation 2025-08-02 12:01:38 -07:00
kexec_core.c kexec: move sysfs entries to /sys/kernel/kexec 2025-11-27 14:24:42 -08:00
kexec_elf.c kexec: initialize ELF lowest address to ULONG_MAX 2025-03-16 22:30:47 -07:00
kexec_file.c x86/kexec: carry forward the boot DTB on kexec 2025-09-13 17:32:43 -07:00
kexec_internal.h kexec: enable CMA based contiguous allocation 2025-08-02 12:01:38 -07:00
kheaders.c kheaders: Simplify attribute through __BIN_ATTR_SIMPLE_RO() 2024-12-24 09:46:49 +01:00
kprobes.c kprobes: Add missing kerneldoc for __get_insn_slot 2025-07-15 18:45:34 +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
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ksysfs.c kexec: move sysfs entries to /sys/kernel/kexec 2025-11-27 14:24:42 -08:00
kthread.c sched: Rename do_set_cpus_allowed() 2025-10-16 11:13:53 +02:00
latencytop.c treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
module_signature.c
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notifier.c
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nscommon.c ns: rename is_initial_namespace() 2025-11-11 10:01:31 +01:00
nsproxy.c nsproxy: fix free_nsproxy() and simplify create_new_namespaces() 2025-11-14 13:10:38 +01:00
nstree.c nstree: fix kernel-doc comments for internal functions 2025-11-14 13:10:38 +01:00
padata.c padata: remove __padata_list_init() 2025-11-14 18:15:49 +08:00
panic.c Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
params.c params: Replace deprecated strcpy() with strscpy() and memcpy() 2025-08-16 21:47:25 +02:00
pid.c ns: drop custom reference count initialization for initial namespaces 2025-11-11 10:01:32 +01:00
pid_namespace.c pid: rely on common reference count behavior 2025-11-11 10:01:32 +01:00
pid_sysctl.h treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
profile.c
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ptrace.c rseq: Introduce struct rseq_data 2025-11-04 08:30:50 +01:00
range.c
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reboot.c - The 7 patch series "powerpc/crash: use generic crashkernel 2025-04-01 10:06:52 -07:00
regset.c
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relay.c relay: update relay to use mmap_prepare 2025-11-16 17:28:11 -08:00
resource.c Reinstate "resource: avoid unnecessary lookups in find_next_iomem_res()" 2025-11-27 14:24:45 -08:00
resource_kunit.c
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rseq.c rseq: Switch to fast path processing on exit to user 2025-11-04 08:34:39 +01:00
scftorture.c scftorture: Handle NULL argument passed to scf_add_to_free_list(). 2024-11-14 16:09:51 -08:00
scs.c scs: fix a wrong parameter in __scs_magic 2025-11-12 10:00:13 -08:00
seccomp.c Performance events updates for v6.18: 2025-09-30 11:11:21 -07:00
signal.c signal: Move MMCID exit out of sighand lock 2025-11-25 19:45:40 +01:00
smp.c smp: Introduce a helper function to check for pending IPIs 2025-11-19 18:06:50 +01:00
smpboot.c sched/smp: Use the SMP version of idle_thread_set_boot_cpu() 2025-06-13 08:47:20 +02:00
smpboot.h
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softirq.c softirq: Allow to drop the softirq-BKL lock on PREEMPT_RT 2025-09-17 16:25:41 +02:00
stacktrace.c
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static_call.c
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static_call_inline.c Modules changes for 6.15-rc1 2025-03-30 15:44:36 -07:00
stop_machine.c sched/core: Fix migrate_swap() vs. hotplug 2025-07-01 15:02:03 +02:00
sys.c Patch series in this pull request: 2025-10-02 18:44:54 -07:00
sys_ni.c uprobes/x86: Add uprobe syscall to speed up uprobe 2025-08-21 20:09:20 +02:00
sysctl-test.c sysctl: move u8 register test to lib/test_sysctl.c 2025-04-14 14:13:41 +02:00
sysctl.c sysctl: Wrap do_proc_douintvec with the public function proc_douintvec_conv 2025-11-27 15:45:38 +01:00
task_work.c task_work: Fix NMI race condition 2025-10-29 10:29:54 +01:00
taskstats.c
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torture.c torture: Delay CPU-hotplug operations until boot completes 2025-08-14 15:26:30 -07:00
tracepoint.c tracepoint: Print the function symbol when tracepoint_debug is set 2025-03-21 15:30:10 -04:00
tsacct.c pid: change bacct_add_tsk() to use task_ppid_nr_ns() 2025-08-19 13:38:20 +02:00
ucount.c ucount: use atomic_long_try_cmpxchg() in atomic_long_inc_below() 2025-08-02 12:01:38 -07:00
uid16.c
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uid16.h
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umh.c treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
up.c
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user-return-notifier.c
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user.c ns: drop custom reference count initialization for initial namespaces 2025-11-11 10:01:32 +01:00
user_namespace.c ns: move ns type into struct ns_common 2025-09-25 09:23:54 +02:00
utsname.c namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
utsname_sysctl.c treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
vhost_task.c vhost: Take a reference on the task in struct vhost_task. 2025-09-21 17:44:20 -04:00
vmcore_info.c vmcoreinfo: track and log recoverable hardware errors 2025-11-27 14:24:44 -08:00
watch_queue.c watch_queue: Use local kmap in post_one_notification() 2025-11-19 12:17:28 +01:00
watchdog.c Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
watchdog_buddy.c watchdog: fix opencoded cpumask_next_wrap() in watchdog_next_cpu() 2025-07-31 11:28:03 -04:00
watchdog_perf.c watchdog: skip checks when panic is in progress 2025-09-13 17:32:53 -07:00
workqueue.c workqueue: Don't rely on wq->rescuer to stop rescuer 2025-11-21 09:45:36 -10:00
workqueue_internal.h
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