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Difference between revisions of "Cpuinfo"

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= CPU capability problem =
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Because CRIU allows to live migrate containers (see [[live migration]] for details), it might happen that CPU a container has been ran on differs from the target CPU. For most software this is usually not a problem, but if a program is compiled with optimizations involving a particular CPU feature (say, AVX instruction), the lack of the feature on a destination machine will lead to execution exception in a best case scenario.
  
Because CRIU allows to live migrate containers (see [[Live_migration | Live migration]] for details) it might happen that CPU a container has been ran on differ from the target CPU. For typical programs this might be not a problem but if a program get compiled with optimization which use a particular CPU feature (say AVX instruction and etc) the lack of the feature on a destination machine will lead to execution exception in a best case.
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Therefore there should be a way to test if destination machine is capable of running container to be migrated. This is the purpose of <code>cpuinfo</code> command.
 
 
Thus there should be a way to test if destination machine is capable of running container being migrated.
 
  
 
== Saving CPU capabilities into an image file ==
 
== Saving CPU capabilities into an image file ==
  
CRIU does not write CPU capabilities into an image by default in a sake of speed. Instead one have to run CRIU as
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CRIU does not write CPU capabilities into an image by default (for the sake of speed). Instead, one have to run CRIU as:
  
 
   criu cpuinfo dump
 
   criu cpuinfo dump
  
to produce ''cpuinfo'' image file which consists of the running CPU information and bits representing the supported capabilities.
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The command creates a ''cpuinfo'' image file, containing information about the current CPU and some bits representing the supported capabilities.
  
 
== Testing CPU capabilities ==
 
== Testing CPU capabilities ==
  
To check if the capabilities saved in ''cpuinfo'' image file is match to the current CPU one should run
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To check if the capabilities saved in ''cpuinfo'' image file are matching those of the current CPU, one should run:
  
 
   criu cpuinfo check
 
   criu cpuinfo check
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== Checkpoint/Restore with CPU capabilities ==
 
== Checkpoint/Restore with CPU capabilities ==
  
While by default CRIU does not save CPU capabilities in image file one can pass '''--cpu-cap''' option to force CRIU to save and check CPU capabilities on dump and restore accordingly.
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While by default CRIU does not save CPU capabilities in image file, one can pass <code>--cpu-cap</code> option to force CRIU to save and check CPU capabilities on dump and restore accordingly.
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[[Category:API]]

Latest revision as of 08:17, 9 January 2018

Because CRIU allows to live migrate containers (see live migration for details), it might happen that CPU a container has been ran on differs from the target CPU. For most software this is usually not a problem, but if a program is compiled with optimizations involving a particular CPU feature (say, AVX instruction), the lack of the feature on a destination machine will lead to execution exception in a best case scenario.

Therefore there should be a way to test if destination machine is capable of running container to be migrated. This is the purpose of cpuinfo command.

Saving CPU capabilities into an image fileEdit

CRIU does not write CPU capabilities into an image by default (for the sake of speed). Instead, one have to run CRIU as:

 criu cpuinfo dump

The command creates a cpuinfo image file, containing information about the current CPU and some bits representing the supported capabilities.

Testing CPU capabilitiesEdit

To check if the capabilities saved in cpuinfo image file are matching those of the current CPU, one should run:

 criu cpuinfo check

Checkpoint/Restore with CPU capabilitiesEdit

While by default CRIU does not save CPU capabilities in image file, one can pass --cpu-cap option to force CRIU to save and check CPU capabilities on dump and restore accordingly.