euleros inclusion
category: feature
bugzilla: NA
CVE: NA

--------------------------------

Support the vcpu_is_preempted() functionality under KVM/arm64. This will
enhance lock performance on overcommitted hosts (more runnable vCPUs
than physical CPUs in the system) as doing busy waits for preempted
vCPUs will hurt system performance far worse than early yielding.

unix benchmark result:
  host:  kernel 4.19.87, HiSilicon Kunpeng920, 8 CPUs
  guest: kernel 4.19.87, 16 vCPUs

               test-case                |    after-patch    |   before-patch
----------------------------------------+-------------------+------------------
 Dhrystone 2 using register variables   | 338955728.5 lps   | 339266319.5 lps
 Double-Precision Whetstone             |     30634.9 MWIPS |     30884.4 MWIPS
 Execl Throughput                       |      6753.2 lps   |      3580.1 lps
 File Copy 1024 bufsize 2000 maxblocks  |    490048.0 KBps  |    313282.3 KBps
 File Copy 256 bufsize 500 maxblocks    |    129662.5 KBps  |     83550.7 KBps
 File Copy 4096 bufsize 8000 maxblocks  |   1552551.5 KBps  |    814327.0 KBps
 Pipe Throughput                        |   8976422.5 lps   |   9048628.4 lps
 Pipe-based Context Switching           |    258641.7 lps   |    252925.9 lps
 Process Creation                       |      5312.2 lps   |      4507.9 lps
 Shell Scripts (1 concurrent)           |      8704.2 lpm   |      6720.9 lpm
 Shell Scripts (8 concurrent)           |      1708.8 lpm   |       607.2 lpm
 System Call Overhead                   |   3714444.7 lps   |   3746386.8 lps
----------------------------------------+-------------------+------------------
 System Benchmarks Index Score          |      2270.6       |      1679.2
Signed-off-by: NZengruan Ye <yezengruan@huawei.com>
Reviewed-by: Nzhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>