(cache)Virtual Machine is extremely slow

Virtual Machine is extremely slow

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Applies to:
- Parallels Access
- Parallels Desktop for Mac Home Edition
Last Review: Jul 11, 2019
Available Translations:
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Symptoms

Windows 7/8 takes a lot of time to start, overall performance is very bad.
Windows 7/8 takes 100% CPU when launched.

Resolution

Download trace_intr from attach to the Desktop.
Start your Virtual Machine
Open Terminal.app and execute:
```
cd ~/Desktop

sudo chmod +x trace_intr 
```
(enter your Mac OS X administrator password)
```
sudo su
```
(enter your Mac OS X administrator password if prompted)
Drag&drop trace_intr from Desktop to Terminal window and then add "1", so it appears as
```
/Users/<username>/Desktop/trace_intr 1 
```
(hit Enter to run utility)

At the output check if any driver takes improper amount (>100000) of interruptions per second. For instance:

VECTOR  CPU#0   CPU#1   TOTAL   DEVNAME                 DRVNAME 
41      0       0       0       HPET                    com.apple.driver.AppleHPET
42      1768    0       1768    HPET                    com.apple.driver.AppleHPET
43      0       0       0       HPET                    com.apple.driver.AppleHPET
46      0       0       0       SMC                     com.apple.driver.AppleSMC
48      0       0       0       HPET                    com.apple.driver.AppleHPET
49      0       0       0       MacBookPro5,2           com.apple.driver.AppleACPIPlatform
4d      0       0       0       MATH                            
50      0       0       0       RP01@C                  com.apple.iokit.IOPCIFamily
                                GFX0@0                  com.apple.GeForce
                                IGPU@0                  com.apple.GeForce
                                Z003                            
                                LGPU                            
51      0       0       0       OHC1@4                  com.apple.driver.AppleUSBOHCI
                                GIGE@A                  com.apple.nvenet
                                LUS0                            
                                LMAC                            
52      422     0       422     OHC2@6                  com.apple.driver.AppleUSBOHCI
                                SATA@B                  com.apple.driver.AppleAHCIPort
                                Z000                            
                                LSI0                            
53      0       0       0       RP05@16                 com.apple.iokit.IOPCIFamily
                                FRWR@0                  com.apple.driver.AppleFWOHCI
                                Z00J                            
54      0       0       0       HDEF@8                  com.apple.driver.AppleHDAController
                                LAZA                            
55      0       0       0       RP04@15                 com.apple.iokit.IOPCIFamily
                                ARPT@0                  com.apple.driver.AirPort.Brcm4331
                                Z00F                            
56      0       0       0       SBUS@3,2                com.apple.driver.AppleSMBusPCI
                                EHC1@4,1                com.apple.driver.AppleUSBEHCI
                                LSMB                            
                                LUS2                            
57      0       0       0       NVPM@3,5                com.apple.driver.NVSMU
                                EHC2@6,1                com.apple.driver.AppleUSBEHCI
                                LPMU                            
                                Z001                            
90      0       0       0       RP06@17                 com.apple.iokit.IOPCIFamily
91      0       0       0       GIGE@A                  com.apple.nvenet
92      0       0       0       SATA@B                  com.apple.driver.AppleAHCIPort
93      78      0       78      IGPU@0                  com.apple.GeForce
94      354996  0       354996  FRWR@0                  com.apple.driver.AppleFWOHCI
95      0       0       0       GFX0@0                  com.apple.GeForce
96      214     0       214     ARPT@0                  com.apple.driver.AirPort.Brcm4331
d2      0       0       0       LAPIC_NMI                       
d7      0       0       0       LAPIC_PM                        
d8      0       0       0       LAPIC_PMC_SW                    
d9      0       0       0       LAPIC_CMCI                      
da      0       0       0       LAPIC_SPURIOUS                  
db      0       0       0       LAPIC_ERROR                     
dc      0       0       0       LAPIC_THERMAL                   
dd      53932   60495   114427  LAPIC_TIMER                     
de      1534    1280    2814    LAPIC_IPI                       
df      0       0       0       LAPIC_PERFCNT

Here the problem is driver:

94      354996  0       354996  FRWR@0            com.apple.driver.AppleFWOHCI

NOTE: this is just an example. Do not unload this partilucar kext driver

Press Control+C to quit the process.
Use the solution from KB 122767

Cause

An interrupt storm on Mac OS X causes bad performance for guest OS.

When virtual machine is running each interrupt request costs a lot more CPU time. This is the overhead of virtualization. Normally, there are several thousands of interrupt requests per second so you don't notice them. But when there are hundreds of thousands of these requests the CPU spends all the time dealing with them.

#- INTERNAL (content below this line is not visible in published article) -

On host OSX versions below 10.8 we could rebin virtual CPUs to mitigate the interrupt storm.

Bind flag syntax:

vm.vcpu<vcpu #>bind=<pcpu #>

e.g.

    vm.vcpu0bind=1

pcpu is the number of physical CPU (whereas vcpu is a number of virtual cpu) and can be anything but 0 (CPU#0 handles external interrupts).

Due to kernel ASLR technique appeared in 10.8 VCPU binding doesn't work anymore and is disabled for these hosts. So we have no methods to mitigate interrupt storms on 10.8/10.9 except for filing bugs to Apple and hoping that they'll fix the issue.

Deleted steps 7 and 8:

In order to unload the driver from Mac OS X, please type in Terminal:
```
sudo kextunload -b
```
then append the name of the driver that is causing the issue, for example com.apple.driver.AppleFWOHCI (as in step 3)

the resulting string will look similar to this:
```
sudo kextunload -b com.apple.driver.AppleFWOHCI 
```
Restart/launch the virtual machine and see if there is any changes in performance.

NOTE: this is just an example. Do not unload this partilucar kext driver NOTE: Not every driver may be unloaded from Mac OS X system. Please perform the unload at your own risk, or contact Apple support for further assistance if you suspect an interrupt storm on your Mac.

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