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3942a9bd7b
linux/kernel
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Peter Zijlstra 3942a9bd7b locking, rcu, cgroup: Avoid synchronize_sched() in __cgroup_procs_write() 
The current percpu-rwsem read side is entirely free of serializing insns
at the cost of having a synchronize_sched() in the write path.

The latency of the synchronize_sched() is too high for cgroups. The
commit 1ed1328792 talks about the write path being a fairly cold path
but this is not the case for Android which moves task to the foreground
cgroup and back around binder IPC calls from foreground processes to
background processes, so it is significantly hotter than human initiated
operations.

Switch cgroup_threadgroup_rwsem into the slow mode for now to avoid the
problem, hopefully it should not be that slow after another commit:

  80127a3968 ("locking/percpu-rwsem: Optimize readers and reduce global impact").

We could just add rcu_sync_enter() into cgroup_init() but we do not want
another synchronize_sched() at boot time, so this patch adds the new helper
which doesn't block but currently can only be called before the first use.

Reported-by: John Stultz <john.stultz@linaro.org>
Reported-by: Dmitry Shmidt <dimitrysh@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Colin Cross <ccross@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rom Lemarchand <romlem@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Todd Kjos <tkjos@google.com>
Link: http://lkml.kernel.org/r/20160811165413.GA22807@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-08-18 15:36:59 +02:00
..
bpf Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2016-07-27 12:03:20 -07:00
configs config: add android config fragments 2016-08-02 19:35:42 -04:00
debug mm/init: Add 'rodata=off' boot cmdline parameter to disable read-only kernel mappings 2016-02-22 08:51:37 +01:00
events perf/core: Change log level for duration warning to KERN_INFO 2016-08-02 10:23:57 +02:00
gcov gcov: add support for gcc version >= 6 2016-07-15 14:54:27 +09:00
irq genirq: Fix missing irq allocation affinity hint 2016-07-19 10:49:47 +02:00
livepatch modules: add ro_after_init support 2016-08-04 10:16:55 +09:30
locking locking/percpu-rwsem: Optimize readers and reduce global impact 2016-08-10 14:34:01 +02:00
power mm, vmscan: move LRU lists to node 2016-07-28 16:07:41 -07:00
printk Revert "printk: create pr_<level> functions" 2016-08-09 10:48:18 -07:00
rcu locking, rcu, cgroup: Avoid synchronize_sched() in __cgroup_procs_write() 2016-08-18 15:36:59 +02:00
sched xen: features and fixes for 4.8-rc0 2016-07-27 11:35:37 -07:00
time Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-07-29 13:55:30 -07:00
trace block: rename bio bi_rw to bi_opf 2016-08-07 14:41:02 -06:00
.gitignore
acct.c
async.c
audit_fsnotify.c wrappers for ->i_mutex access 2016-01-22 18:04:28 -05:00
audit_tree.c audit: cleanup prune_tree_thread 2016-04-04 09:46:47 -04:00
audit_watch.c don't bother with ->d_inode->i_sb - it's always equal to ->d_sb 2016-04-10 17:11:51 -04:00
audit.c Merge branch 'stable-4.8' of git://git.infradead.org/users/pcmoore/audit 2016-07-29 17:54:17 -07:00
audit.h Merge branch 'stable-4.8' of git://git.infradead.org/users/pcmoore/audit 2016-07-29 17:54:17 -07:00
auditfilter.c audit: add fields to exclude filter by reusing user filter 2016-06-27 11:01:00 -04:00
auditsc.c Merge branch 'stable-4.8' of git://git.infradead.org/users/pcmoore/audit 2016-07-29 17:54:17 -07:00
backtracetest.c
bounds.c
capability.c kernel: Add noaudit variant of ns_capable() 2016-06-06 20:16:18 +10:00
cgroup_freezer.c
cgroup_pids.c cgroup: Use lld instead of ld when printing pids controller events_limit 2016-06-21 15:03:36 -04:00
cgroup.c locking, rcu, cgroup: Avoid synchronize_sched() in __cgroup_procs_write() 2016-08-18 15:36:59 +02:00
compat.c
configs.c
context_tracking.c
cpu_pm.c
cpu.c timers/core: Correct callback order during CPU hot plug 2016-07-28 18:56:22 +02:00
cpuset.c cpuset, mm: fix TIF_MEMDIE check in cpuset_change_task_nodemask 2016-07-28 16:07:41 -07:00
crash_dump.c
cred.c cred: Reject inodes with invalid ids in set_create_file_as() 2016-06-30 18:05:09 -05:00
delayacct.c kmemcg: account certain kmem allocations to memcg 2016-01-14 16:00:49 -08:00
dma.c
elfcore.c
exec_domain.c
exit.c kernel/exit.c: quieten greatest stack depth printk 2016-08-02 19:35:23 -04:00
extable.c
fork.c mm: fix memcg stack accounting for sub-page stacks 2016-07-28 16:07:41 -07:00
freezer.c freezer, oom: check TIF_MEMDIE on the correct task 2016-07-28 16:07:41 -07:00
futex_compat.c ptrace: use fsuid, fsgid, effective creds for fs access checks 2016-01-20 17:09:18 -08:00
futex.c futex: Assume all mappings are private on !MMU systems 2016-07-29 18:44:14 +02:00
groups.c
hung_task.c kernel/hung_task.c: use timeout diff when timeout is updated 2016-03-22 15:36:02 -07:00
irq_work.c
jump_label.c powerpc updates for 4.8 #2 2016-08-05 09:00:54 -04:00
kallsyms.c kallsyms: add support for relative offsets in kallsyms address table 2016-03-15 16:55:16 -07:00
kcmp.c ptrace: use fsuid, fsgid, effective creds for fs access checks 2016-01-20 17:09:18 -08:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c kernel/kcov: unproxify debugfs file's fops 2016-06-15 04:56:35 -07:00
kexec_core.c kexec: add restriction on kexec_load() segment sizes 2016-08-02 19:35:31 -04:00
kexec_file.c kexec: introduce a protection mechanism for the crashkernel reserved memory 2016-05-23 17:04:14 -07:00
kexec_internal.h kexec: move some memembers and definitions within the scope of CONFIG_KEXEC_FILE 2016-01-20 17:09:18 -08:00
kexec.c kexec: allow architectures to override boot mapping 2016-08-02 19:35:27 -04:00
kmod.c
kprobes.c
ksysfs.c kexec: add a kexec_crash_loaded() function 2016-08-02 19:35:30 -04:00
kthread.c
latencytop.c sched/debug: Make schedstats a runtime tunable that is disabled by default 2016-02-09 11:54:23 +01:00
Makefile ELF/MIPS build fix 2016-05-23 17:04:14 -07:00
membarrier.c
memremap.c libnvdimm for 4.8 2016-07-28 17:38:16 -07:00
module_signing.c KEYS: Move the point of trust determination to __key_link() 2016-04-11 22:43:43 +01:00
module-internal.h
module.c Removed the MODULE_SIG_FORCE-means-no-MODULE_FORCE_LOAD patch. 2016-08-04 09:14:38 -04:00
notifier.c
nsproxy.c cgroup: introduce cgroup namespaces 2016-02-16 13:04:58 -05:00
padata.c kernel/padata.c: hide unused functions 2016-05-19 19:12:14 -07:00
panic.c kexec: use core_param for crash_kexec_post_notifiers boot option 2016-08-02 19:35:29 -04:00
params.c
pid_namespace.c
pid.c remove lots of IS_ERR_VALUE abuses 2016-05-27 15:26:11 -07:00
profile.c profile: Convert to hotplug state machine 2016-07-15 10:41:42 +02:00
ptrace.c tree-wide: replace config_enabled() with IS_ENABLED() 2016-08-04 08:50:07 -04:00
range.c
reboot.c
relay.c relay: add global mode support for buffer-only channels 2016-08-02 19:35:41 -04:00
resource.c /proc/iomem: only expose physical resource addresses to privileged users 2016-04-14 12:56:09 -07:00
seccomp.c tree-wide: replace config_enabled() with IS_ENABLED() 2016-08-04 08:50:07 -04:00
signal.c signals: Use hrtimer for sigtimedwait() 2016-07-07 10:35:07 +02:00
smp.c Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-07-29 13:55:30 -07:00
smpboot.c cpu/hotplug: Unpark smpboot threads from the state machine 2016-03-01 20:36:56 +01:00
smpboot.h cpu/hotplug: Create hotplug threads 2016-03-01 20:36:56 +01:00
softirq.c arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections 2016-03-25 16:37:42 -07:00
stacktrace.c
stop_machine.c stop_machine: Touch_nmi_watchdog() after MULTI_STOP_PREPARE 2016-07-27 11:12:11 +02:00
sys_ni.c
sys.c prctl: make PR_SET_THP_DISABLE wait for mmap_sem killable 2016-05-23 17:04:14 -07:00
sysctl_binary.c kernel/sysctl_binary.c: use generic UUID library 2016-05-20 17:58:30 -07:00
sysctl.c printk: add kernel parameter to control writes to /dev/kmsg 2016-08-02 19:35:06 -04:00
task_work.c task_work: use READ_ONCE/lockless_dereference, avoid pi_lock if !task_works 2016-08-02 19:35:02 -04:00
taskstats.c taskstats: use the libnl API to align nlattr on 64-bit 2016-04-23 20:13:25 -04:00
test_kprobes.c
torture.c torture: Stop onoff task if there is only one cpu 2016-06-14 16:03:28 -07:00
tracepoint.c kernel/...: convert pr_warning to pr_warn 2016-03-22 15:36:02 -07:00
tsacct.c time, acct: Drop irq save & restore from __acct_update_integrals() 2016-02-29 09:53:09 +01:00
uid16.c
up.c
user_namespace.c fs: Limit file caps to the user namespace of the super block 2016-06-24 10:40:31 -05:00
user-return-notifier.c
user.c
utsname_sysctl.c
utsname.c
watchdog.c Revert "perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86" 2016-07-10 20:58:36 +02:00
workqueue_internal.h sched/core: Get rid of 'cpu' argument in wq_worker_sleeping() 2016-03-02 10:28:47 -05:00
workqueue.c Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-07-29 13:55:30 -07:00