Davidlohr Bueso
1d0dcb3ad9
futex: Implement lockless wakeups ...
Given the overall futex architecture, any chance of reducing
hb->lock contention is welcome. In this particular case, using
wake-queues to enable lockless wakeups addresses very much real
world performance concerns, even cases of soft-lockups in cases
of large amounts of blocked tasks (which is not hard to find in
large boxes, using but just a handful of futex).
At the lowest level, this patch can reduce latency of a single thread
attempting to acquire hb->lock in highly contended scenarios by a
up to 2x. At lower counts of nr_wake there are no regressions,
confirming, of course, that the wake_q handling overhead is practically
non existent. For instance, while a fair amount of variation,
the extended pef-bench wakeup benchmark shows for a 20 core machine
the following avg per-thread time to wakeup its share of tasks:
nr_thr ms-before ms-after
16 0.0590 0.0215
32 0.0396 0.0220
48 0.0417 0.0182
64 0.0536 0.0236
80 0.0414 0.0097
96 0.0672 0.0152
Naturally, this can cause spurious wakeups. However there is no core code
that cannot handle them afaict, and furthermore tglx does have the point
that other events can already trigger them anyway.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Mason <clm@fb.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: George Spelvin <linux@horizon.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1430494072-30283-3-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-05-08 12:21:40 +02:00
bpf: fix 64-bit divide
2015-04-27 23:11:49 -04:00
x86: Add "make tinyconfig" to configure the tiniest possible kernel
2014-08-08 16:30:24 -07:00
debug: prevent entering debug mode on panic/exception.
2015-02-19 12:39:03 -06:00
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next
2015-04-15 09:00:47 -07:00
gcov: fix softlockups
2015-04-17 09:04:08 -04:00
irqchip core change for v4.1 (round 3)
2015-04-11 11:17:28 +02:00
Merge branch 'for-4.1/core-noarch' into for-linus
2015-04-13 23:57:20 +02:00
sched: Handle priority boosted tasks proper in setscheduler()
2015-05-08 11:53:55 +02:00
Merge back earlier suspend/hibernate material for v4.1.
2015-04-10 12:01:59 +02:00
TTY/Serial patches for 4.1-rc1
2015-04-21 09:33:10 -07:00
rcu: Control grace-period delays directly from value
2015-04-14 19:33:59 -07:00
sched: Implement lockless wake-queues
2015-05-08 12:20:45 +02:00
sched, timer: Use the atomic task_cputime in thread_group_cputimer
2015-05-08 12:17:46 +02:00
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2015-04-26 17:22:07 -07:00
acct: check FMODE_CAN_WRITE
2015-04-11 22:27:55 -04:00
kernel/async.c: switch to pr_foo()
2014-10-09 22:26:04 -04:00
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2015-04-26 17:22:07 -07:00
Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit
2015-04-22 14:49:23 -07:00
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2015-04-26 17:22:07 -07:00
VFS: audit: d_backing_inode() annotations
2015-04-15 15:06:55 -04:00
Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit
2015-02-11 20:07:47 -08:00
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2015-04-26 17:22:07 -07:00
page-cgroup: get rid of NR_PCG_FLAGS
2014-08-08 15:57:18 -07:00
kernel: conditionally support non-root users, groups and capabilities
2015-04-15 16:35:22 -07:00
cgroup: remove use of seq_printf return value
2015-04-15 16:35:25 -07:00
all arches, signal: move restart_block to struct task_struct
2015-02-12 18:54:12 -08:00
context_tracking: Export context_tracking_user_enter/exit
2015-03-09 15:43:00 +01:00
Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2015-04-14 13:36:04 -07:00
kernel, cpuset: remove exception for __GFP_THISNODE
2015-04-14 16:49:03 -07:00
crash_dump: Make is_kdump_kernel() accessible from modules
2014-08-25 15:42:19 -07:00
kernel: conditionally support non-root users, groups and capabilities
2015-04-15 16:35:22 -07:00
Remove rest of exec domains.
2015-04-12 21:03:31 +02:00
Remove execution domain support
2015-04-12 20:58:24 +02:00
ftrace/x86/extable: Add is_ftrace_trampoline() function
2014-11-19 15:25:26 -05:00
sched, timer: Replace spinlocks with atomics in thread_group_cputimer(), to improve scalability
2015-05-08 12:15:31 +02:00
freezer: remove obsolete comments in __thaw_task()
2014-10-21 23:44:20 +02:00
futex: Implement lockless wakeups
2015-05-08 12:21:40 +02:00
kernel: conditionally support non-root users, groups and capabilities
2015-04-15 16:35:22 -07:00
kernel/hung_task.c: change hung_task.c to use for_each_process_thread()
2015-04-15 16:35:22 -07:00
percpu: Convert remaining __get_cpu_var uses in 3.18-rcX
2014-10-29 11:18:18 -04:00
kernel/kallsyms.c: use __seq_open_private()
2014-10-14 02:18:16 +02:00
kcmp: fix standard comparison bug
2014-09-10 15:42:12 -07:00
locking/mcs: Better differentiate between MCS variants
2015-01-14 15:07:32 +01:00
kexec: allocate the kexec control page with KEXEC_CONTROL_MEMORY_GFP
2015-04-23 16:52:01 +02:00
usermodehelper: kill the kmod_thread_locker logic
2014-12-10 17:41:17 -08:00
kprobes: makes kprobes/enabled works correctly for optimized kprobes.
2015-02-13 21:21:42 -08:00
kernel/kthread.c: partial revert of 81c98869fa ("kthread: ensure locality of task_struct allocations")
2014-10-09 22:25:51 -04:00
modsign: change default key details
2015-04-30 09:35:41 -07:00
Quentin opened a can of worms by adding extable entry checking to modpost,
2015-04-22 09:49:24 -07:00
rcu: Make SRCU optional by using CONFIG_SRCU
2015-01-06 11:04:29 -08:00
bury struct proc_ns in fs/proc
2014-12-04 14:34:54 -05:00
padata: use %*pb[l] to print bitmaps including cpumasks and nodemasks
2015-02-13 21:21:38 -08:00
livepatch: kernel: add TAINT_LIVEPATCH
2014-12-22 15:40:48 +01:00
params: handle quotes properly for values not of form foo="bar".
2015-04-15 13:31:23 +09:30
fork: report pid reservation failure properly
2015-04-17 09:04:06 -04:00
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2014-12-16 15:53:03 -08:00
profile: use %*pb[l] to print bitmaps including cpumasks and nodemasks
2015-02-13 21:21:38 -08:00
ptrace: ptrace_detach() can no longer race with SIGKILL
2015-04-17 09:04:06 -04:00
kernel: avoid overflow in cmp_range
2015-01-17 10:02:23 +13:00
kernel/reboot.c: add orderly_reboot for graceful reboot
2015-04-15 16:35:23 -07:00
VFS: kernel/: d_inode() annotations
2015-04-15 15:06:55 -04:00
kernel/resource.c: remove deprecated __check_region() and friends
2015-04-15 16:35:22 -07:00
seccomp: cap SECCOMP_RET_ERRNO data to MAX_ERRNO
2015-02-17 14:34:55 -08:00
signals, sched: Change all uses of JOBCTL_* from 'int' to 'long'
2015-05-08 12:04:36 +02:00
smp: Fix error case handling in smp_call_function_*()
2015-04-19 13:19:23 -07:00
smpboot: Add common code for notification from dying CPU
2015-03-11 13:20:25 -07:00
Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2015-02-09 15:24:03 -08:00
stacktrace: introduce snprint_stack_trace for buffer output
2014-12-13 12:42:48 -08:00
prctl: avoid using mmap_sem for exe_file serialization
2015-04-17 09:04:07 -04:00
kernel: conditionally support non-root users, groups and capabilities
2015-04-15 16:35:22 -07:00
kernel/sysctl.c: detect overflows when converting to int
2015-04-17 09:04:08 -04:00
kernel: add panic_on_warn
2014-12-10 17:41:10 -08:00
netlink: make nlmsg_end() and genlmsg_end() void
2015-01-18 01:03:45 -05:00
kernel/test_kprobes.c: use current logging functions
2014-08-08 15:57:18 -07:00
torture: Address race in module cleanup
2014-09-16 13:41:06 -07:00
groups: Consolidate the setgroups permission checks
2014-12-05 17:19:27 -06:00
scheduler: Replace __get_cpu_var with this_cpu_ptr
2014-08-26 13:45:45 -04:00
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
2014-12-17 12:31:40 -08:00
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
2014-12-17 12:31:40 -08:00
copy address of proc_ns_ops into ns_common
2014-12-04 14:34:47 -05:00
Merge branch 'akpm' (patches from Andrew)
2015-04-14 16:49:17 -07:00
workqueue: Reorder sysfs code
2015-04-06 11:16:04 -04:00
1d0dcb3ad9