OpenE2K
/
linux
6
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity
849,691 Commits 4 Branches 0 Tags 2 GiB
C 97.7%
Assembly 1.3%
Makefile 0.4%
Shell 0.3%
Python 0.1%
Other 0.1%
Go to file
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
Documentation Documentation: move Documentation/virtual to Documentation/virt 2019-07-24 10:52:11 +02:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch KVM: X86: Boost queue head vCPU to mitigate lock waiter preemption 2019-07-24 13:56:53 +02:00
block for-5.3/block-20190708 2019-07-09 10:45:06 -07:00
certs Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs" 2019-07-10 18:43:43 -07:00
crypto USB / PHY patches for 5.3-rc1 2019-07-11 15:40:06 -07:00
drivers Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
fs dlm for 5.3 2019-07-12 17:37:53 -07:00
include Documentation: move Documentation/virtual to Documentation/virt 2019-07-24 10:52:11 +02:00
init Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
ipc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
kernel KVM: LAPIC: Inject timer interrupt via posted interrupt 2019-07-20 09:00:40 +02:00
lib Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
mm Driver Core and debugfs changes for 5.3-rc1 2019-07-12 12:24:03 -07:00
net 9p pull request for inclusion in 5.13 2019-07-12 17:31:19 -07:00
samples Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
scripts Kconfig updates for v5.3 2019-07-12 16:06:27 -07:00
security Merge branch 'akpm' (patches from Andrew) 2019-07-12 11:40:28 -07:00
sound Driver Core and debugfs changes for 5.3-rc1 2019-07-12 12:24:03 -07:00
tools Documentation: move Documentation/virtual to Documentation/virt 2019-07-24 10:52:11 +02:00
usr kbuild: compile-test exported headers to ensure they are self-contained 2019-07-08 23:13:57 +09:00
virt Documentation: move Documentation/virtual to Documentation/virt 2019-07-24 10:52:11 +02:00
.clang-format Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 11:26:25 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: do not create wrappers for header-test-y 2019-07-09 10:10:27 +09:00
.mailmap MAINTAINERS: Update my email address 2019-06-18 14:37:27 +01:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-06-25 01:32:59 +02:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Documentation: move Documentation/virtual to Documentation/virt 2019-07-24 10:52:11 +02:00
Makefile Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.