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 bits representing the capabilities current CPU support.
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The command creates a ''cpuinfo'' image file, containing information about the current CPU and some bits representing the supported capabilities.
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== Testing CPU capabilities ==
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To check if the capabilities saved in ''cpuinfo'' image file are matching those of the current CPU, one should run:
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  criu cpuinfo check
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== Checkpoint/Restore with CPU capabilities ==
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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 file[edit]

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 capabilities[edit]

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 capabilities[edit]

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.