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If guest kernel is configured with nopvspin, or CONFIG_PARAVIRT_SPINLOCK
is disabled, or guest find its has dedicated pCPUs from realtime hint
feature, the pvspinlock will be disabled, and vCPU preemption check
is disabled too.
Hoever, KVM still can emulating HLT for vCPU for both cases. Checking if a vCPU
is preempted or not can still boost performance in IPI-heavy scenarios such as
unixbench file copy and pipe-based context switching tests: Here the vCPU is
running with a dedicated pCPU, so the guest kernel has nopvspin but is
emulating HLT for the vCPU:
Testcase Base with patch
System Benchmarks Index Values INDEX INDEX
Dhrystone 2 using register variables 3278.4 3277.7
Double-Precision Whetstone 822.8 825.8
Execl Throughput 1296.5 941.1
File Copy 1024 bufsize 2000 maxblocks 2124.2 2142.7
File Copy 256 bufsize 500 maxblocks 1335.9 1353.6
File Copy 4096 bufsize 8000 maxblocks 4256.3 4760.3
Pipe Throughput 1050.1 1054.0
Pipe-based Context Switching 243.3 352.0
Process Creation 820.1 814.4
Shell Scripts (1 concurrent) 2169.0 2086.0
Shell Scripts (8 concurrent) 7710.3 7576.3
System Call Overhead 672.4 673.9
======== =======
System Benchmarks Index Score 1467.2 1483.0
Move the setting of pv_ops.lock.vcpu_is_preempted to kvm_guest_init, so
that it does not depend on pvspinlock.
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Message-Id: <1646815610-43315-1-git-send-email-lirongqing@baidu.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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.