DIT Configuration
- W.Erber
Contents
Introduction
To view or change the current DIT configuration, select DIT in the left-hand pane of the Settings window.
There are three levels of DIT optimization:
OFF: no DIT optimization.
Client JIT or first level DIT: this is the equivalent of the DIT optimization available in older versions.
Server JIT or second level DIT: this is a more aggressive optimization. It optimizes SPARC instructions at runtime, based on an MRU policy (Most Recently Used).
Server JIT is not available on Charon-SSP/4M. Client and server JIT are implemented in two separate images that will be configured automatically by Charon-SSP Manager depending on the configuration.
Comparison between the DIT configuration options:
DIT Optimization | Translation speed | Command execution after Translation | Memory requirements |
|---|---|---|---|
| OFF | n/a | Slow | n/a |
| Client JIT | Fast | Faster | Approx. 2GB RAM |
| Server JIT | Slow | Fastest (depending on application) | Approx. 6GB RAM |
Due to the slower and more resource-consuming translation in Server JIT mode, mostly long-running applications will benefit from Server JIT.
The following sections show the details of both modes.
Client JIT
This section describes the configuration options available in Client JIT mode. The image below shows a sample of the Charon-4U configuration screen.
The following table lists each of the fields available in the DIT Client JIT mode and describes their use.
Virtual machine client JIT configuration fields | |
|---|---|
| Field | Description |
Virtualization Mode | Emulation selects the Charon-SSP/4U or Charon-SSP/4V emulator, Intel VT-x/EPT informs the manager that the hardware prerequisites for running Charon-SSP/4U+ or Charon-SSP/4V+ are met. This option is inactive on Charon-SSP/4M or if Charon-SSP/4U+/4V+ is not installed. Attempting to run Charon-SSP/4U+/4V+ on insufficient hardware will cause the instance to exit with an error message. For example, Check if your host system runs on dedicated hardware if you encounter such errors. |
DIT Optimization | This option controls the Dynamic Instruction Translation (DIT). DIT is a just in time compilation technology to dynamically optimize the SPARC instruction execution on x86-64 platforms. It can be set to OFF, Client JIT, or Server JIT (Charon-4U/4V only). The remainder of this table describes the Client JIT parameters. |
DIT page size | This option controls the size of the translation buffer holding the translated binary code that results from the DIT optimization. It can be increased to a maximum of 2048KB. This parameter should only be changed if the log file indicates that the DIT optimization was disabled because the translation buffer size was too small. This option is not available on Charon-SSP/4M. |
FP boost ratio | Defines the level of floating-point optimization. The parameter can be set to a value from 0 to 100. The default is 0 (= no boost). Most floating-point applications will profit from increasing this ratio. However, some applications may not be compatible with the optimization resulting in degraded performance. So testing is required. This option is not available on Charon-SSP/4M |
Server JIT
This section describes the configuration options available in Server JIT mode (not available on Charon-SSP/4M).
The example below shows a Charon-4U configuration screen:
The following table lists each of the fields available in the DIT Server JIT mode and describes their use.
Virtual machine server JIT configuration fields | |
|---|---|
| Field | Description |
Virtualization Mode | Emulation selects the Charon-SSP/4U or Charon-SSP/4V emulator, Intel VT-x/EPT informs the manager that the hardware prerequisites for running Charon-SSP/4U+ or Charon-SSP/4V+ are met. This option is inactive on Charon-SSP/4M or if Charon-SSP/4U+/4V+ is not installed. Attempting to run Charon-SSP/4U+/4V+ on insufficient hardware will cause the instance to exit with an error message. For example, Check if your host system runs on dedicated hardware if you encounter such errors. |
DIT Optimization | This option controls the Dynamic Instruction Translation (DIT). DIT is a just in time compilation technology to dynamically optimize the SPARC instruction execution on x86-64 platforms. It can be set to OFF, Client JIT, or Server JIT. The remainder of this table describes the Server JIT parameters (not available on Charon-SSP/4M). |
DIT page size | This option controls the size of the translation buffer holding the translated binary code that results from the DIT optimization. It can be increased to a maximum of 2048KB. This parameter should only be changed if the log file indicates that the DIT optimization was disabled because the translation buffer size was too small |
DIT code cache | Size of cache between 1024MB and 8192MB in steps of 1024MB. |
FP boost ratio | Defines the level of floating-point optimization. The parameter can be set to a value from 0 to 100. The default is 0 (= no boost). Most floating-point applications will profit from increasing this ratio. However, some applications may not be compatible with the optimization resulting in degraded performance. So testing is required. |
INT boost ratio | Defines the level of integer operation optimization. The parameter can be set to a value from 0 to 100. The default is 100 (= maximum boost). The higher the value the more resources are required. Hence high values are likely to provide most benefit if the guest system applications run for a long time. |
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