Star64_linux/kernel
Johannes Weiner 204cb79ad4 kernel: sysctl: make drop_caches write-only
Currently, the drop_caches proc file and sysctl read back the last value
written, suggesting this is somehow a stateful setting instead of a
one-time command.  Make it write-only, like e.g.  compact_memory.

While mitigating a VM problem at scale in our fleet, there was confusion
about whether writing to this file will permanently switch the kernel into
a non-caching mode.  This influences the decision making in a tense
situation, where tens of people are trying to fix tens of thousands of
affected machines: Do we need a rollback strategy?  What are the
performance implications of operating in a non-caching state for several
days?  It also caused confusion when the kernel team said we may need to
write the file several times to make sure it's effective ("But it already
reads back 3?").

Link: http://lkml.kernel.org/r/20191031221602.9375-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Chris Down <chris@chrisdown.name>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-12-01 12:59:07 -08:00
..
bpf Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-11-26 16:02:40 -08:00
cgroup
configs
debug
dma dma-mapping updates for 5.5-rc1 2019-11-28 11:16:43 -08:00
events mm/mmap.c: use IS_ERR_VALUE to check return value of get_unmapped_area 2019-12-01 06:29:19 -08:00
gcov
irq
livepatch New tracing features: 2019-11-27 11:42:01 -08:00
locking Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-11-26 16:02:40 -08:00
power Merge branches 'pm-sleep', 'pm-domains', 'pm-opp' and 'powercap' 2019-11-26 10:27:49 +01:00
printk
rcu
sched Power management updates for 5.5-rc1 2019-11-26 19:06:44 -08:00
time Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-11-26 15:42:43 -08:00
trace New tracing features: 2019-11-27 11:42:01 -08:00
.gitignore
acct.c
async.c
audit.c
audit.h
audit_fsnotify.c
audit_tree.c
audit_watch.c
auditfilter.c
auditsc.c
backtracetest.c
bounds.c
capability.c
compat.c
configs.c
context_tracking.c
cpu.c Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-11-26 16:02:40 -08:00
cpu_pm.c
crash_core.c
crash_dump.c
cred.c
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-11-26 16:02:40 -08:00
extable.c
fail_function.c
fork.c fork: support VMAP_STACK with KASAN_VMALLOC 2019-12-01 12:59:05 -08:00
freezer.c
futex.c
gen_kheaders.sh
groups.c
hung_task.c
iomem.c
irq_work.c
jump_label.c
kallsyms.c
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c
kexec.c
kexec_core.c
kexec_elf.c
kexec_file.c
kexec_internal.h
kheaders.c
kmod.c
kprobes.c
ksysfs.c
kthread.c
latencytop.c
Makefile
module-internal.h
module.c New tracing features: 2019-11-27 11:42:01 -08:00
module_signature.c
module_signing.c
notifier.c
nsproxy.c
padata.c
panic.c
params.c
pid.c
pid_namespace.c
profile.c
ptrace.c
range.c
reboot.c
relay.c
resource.c
rseq.c
seccomp.c
signal.c
smp.c
smpboot.c
smpboot.h
softirq.c
stackleak.c
stacktrace.c
stop_machine.c
sys.c
sys_ni.c
sysctl-test.c
sysctl.c kernel: sysctl: make drop_caches write-only 2019-12-01 12:59:07 -08:00
sysctl_binary.c
task_work.c
taskstats.c
test_kprobes.c
torture.c
tracepoint.c
tsacct.c
ucount.c
uid16.c
uid16.h
umh.c
up.c
user-return-notifier.c
user.c
user_namespace.c
utsname.c
utsname_sysctl.c
watchdog.c
watchdog_hld.c
workqueue.c Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-11-26 15:42:43 -08:00
workqueue_internal.h