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− | CRIU can detect what memory pages a task (or tasks) has changed since some moment of time. This page describes why this thing is required, how it works and how to use it. | + | CRIU can detect what memory pages a task (or tasks) has changed since some moment of time. This page describes why this is required, how it works and how to use it. |
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| == Why do we need to track memory changed == | | == Why do we need to track memory changed == |
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− | There are several scenarios when detecting what parts of memory has changed is required: | + | There are several scenarios where detecting what parts of memory has changed is required: |
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| ; [[Incremental dumps]] | | ; [[Incremental dumps]] |
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| # criu check --feature mem_dirty_track | | # criu check --feature mem_dirty_track |
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− | command should say the feature is supported. The memory changes tracking was initially merged into Linux kernel v3.11, and was further polished until v3.18. | + | command should say the feature is supported. The memory changes tracking was initially merged into Linux kernel v3.11, and was further polished until v3.18 (see [[Upstream kernel commits]] for details). |
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| There are several command line options to use the functionality: | | There are several command line options to use the functionality: |
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| ;<code>--prev-images-dir</code> option | | ;<code>--prev-images-dir</code> option |
− | :This option says where the images from previous <code>dump</code> or <code>pre-dump</code> (see below) action reside. If possible, CRIU will not dump memory pages that hasn't changed since that time. | + | :This option is used to provide the path where images from a previous <code>dump</code> or <code>pre-dump</code> (see below) action reside. If possible, CRIU will dump only the memory pages that have been modified since that time. |
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| ;<code>--track-mem</code> option | | ;<code>--track-mem</code> option |
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| ;<code>pre-dump</code> action | | ;<code>pre-dump</code> action |
− | :This action dumps only part of information about processes and does this keeping tasks frozen for minimally possible time. The images generated by pre-dump cannot and should not be used for restore. After this action the proper <code>dump</code> should be performed with properly configured <code>--prev-images-dir</code> path. | + | :This action dumps only part of the information about processes and does that by keeping tasks frozen for the shortest possible time. The images generated by pre-dump cannot and should not be used for restore. After this action the proper <code>dump</code> should be performed with properly configured <code>--prev-images-dir</code> path. |
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| == See also == | | == See also == |