Wanpeng Li 266e85a5ec KVM: X86: Boost queue head vCPU to mitigate lock waiter preemption ... Commit 11752adb (locking/pvqspinlock: Implement hybrid PV queued/unfair locks) introduces hybrid PV queued/unfair locks - queued mode (no starvation) - unfair mode (good performance on not heavily contended lock) The lock waiter goes into the unfair mode especially in VMs with over-commit vCPUs since increaing over-commitment increase the likehood that the queue head vCPU may have been preempted and not actively spinning. However, reschedule queue head vCPU timely to acquire the lock still can get better performance than just depending on lock stealing in over-subscribe scenario. Testing on 80 HT 2 socket Xeon Skylake server, with 80 vCPUs VM 80GB RAM: ebizzy -M vanilla boosting improved 1VM 23520 25040 6% 2VM 8000 13600 70% 3VM 3100 5400 74% The lock holder vCPU yields to the queue head vCPU when unlock, to boost queue head vCPU which is involuntary preemption or the one which is voluntary halt due to fail to acquire the lock after a short spin in the guest. Cc: Waiman Long <longman@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>		2019-07-24 13:56:53 +02:00
..
boot	It's been a relatively busy cycle for docs:	2019-07-09 12:34:26 -07:00
configs	x86/defconfigs: Remove useless UEVENT_HELPER_PATH	2019-06-21 19:22:08 +02:00
crypto	Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6	2019-07-08 20:57:08 -07:00
entry	Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-07-11 13:54:00 -07:00
events	Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-07-09 11:15:52 -07:00
hyperv	clocksource/drivers: Continue making Hyper-V clocksource ISA agnostic	2019-07-03 11:00:59 +02:00
ia32	x86: use static_cpu_has in uaccess region to avoid instrumentation	2019-07-12 11:05:42 -07:00
include	KVM: X86: Dynamically allocate user_fpu	2019-07-22 13:55:48 +02:00
kernel	ARM:	2019-07-12 15:35:14 -07:00
kvm	KVM: X86: Boost queue head vCPU to mitigate lock waiter preemption	2019-07-24 13:56:53 +02:00
lib	Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-07-08 10:39:56 -07:00
math-emu	x86/fpu: Always init the state in fpu__clear()	2019-04-09 19:28:06 +02:00
mm	Driver Core and debugfs changes for 5.3-rc1	2019-07-12 12:24:03 -07:00
net	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2019-07-08 19:48:57 -07:00
oprofile
pci	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 387	2019-06-05 17:37:11 +02:00
platform	Driver Core and debugfs changes for 5.3-rc1	2019-07-12 12:24:03 -07:00
power	SPDX update for 5.2-rc4	2019-06-08 12:52:42 -07:00
purgatory	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 230	2019-06-19 17:09:06 +02:00
ras	RAS/CEC: Add CONFIG_RAS_CEC_DEBUG and move CEC debug features there	2019-06-08 17:39:24 +02:00
realmode
tools	Merge branch 'x86-paravirt-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-07-08 17:34:44 -07:00
um	Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2019-07-08 21:48:15 -07:00
video	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
xen	Driver Core and debugfs changes for 5.3-rc1	2019-07-12 12:24:03 -07:00
.gitignore
Kbuild	treewide: Add SPDX license identifier - Kbuild	2019-05-30 11:32:33 -07:00
Kconfig	mm: rename CONFIG_HAVE_GENERIC_GUP to CONFIG_HAVE_FAST_GUP	2019-07-12 11:05:44 -07:00
Kconfig.cpu	x86/cpu: Create Zhaoxin processors architecture support file	2019-06-22 11:45:57 +02:00
Kconfig.debug	It's been a relatively busy cycle for docs:	2019-07-09 12:34:26 -07:00
Makefile	x86/build: Keep local relocations with ld.lld	2019-04-05 12:34:35 +02:00
Makefile_32.cpu
Makefile.um