Rename @metadata.code.compilation_order to @metadata.code.compilation_priority and update semantics #17
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tlively
approved these changes
Jun 18, 2025
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| The *hotness* attribute has no pre-defined meaning. The larger the value, to more often a function is expected to run. So an engine can simply order the functions by hotness and tier up the ones with the largest *hotness* until the compilation budget is exceeded. The compilation budget might depend on the engine, compiler, available resources, how long the program has been running, etc. The special value of 0 is reserved for functions that only run once (e.g. initialization functions). An engine can decide to interpret those functions only or to free up code space by removing the compiled code after execution. Applications can run such a function multiple times, but they should not because this might come with severe performance penalties, e.g. for repeated recompilation, not ever getting tiered up, etc. | ||
| The *optimization priority* has no clear implication on whether a function is tiered up using a more optimized compiler. The smaller the value, to more often a function is expected to be running. So an engine can simply order the functions by priority and tier up the ones with the smallest *optimization priority* until the compilation budget is exceeded. The compilation budget might depend on the engine, compiler, available resources, how long the program has been running, etc. Using a threshold might look easier but relies heavily on the accuracy of the estimation, making it potentially less reliable. |
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| The *optimization priority* has no clear implication on whether a function is tiered up using a more optimized compiler. The smaller the value, to more often a function is expected to be running. So an engine can simply order the functions by priority and tier up the ones with the smallest *optimization priority* until the compilation budget is exceeded. The compilation budget might depend on the engine, compiler, available resources, how long the program has been running, etc. Using a threshold might look easier but relies heavily on the accuracy of the estimation, making it potentially less reliable. | |
| The *optimization priority* has no clear implication on whether a function is tiered up using a more optimized compiler. The smaller the value, the more often a function is expected to be running. So an engine can simply order the functions by priority and tier up the ones with the smallest *optimization priority* until the compilation budget is exceeded. The compilation budget might depend on the engine, compiler, available resources, how long the program has been running, etc. Using a threshold might look easier but relies heavily on the accuracy of the estimation, making it potentially less reliable. |
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| and tools can produce one or the other. | ||
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| To produce the special value of 127 for the optimization value, one can pass `run_once` without any number instead of the `optimization` annotation. |
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It would be nice to include an example of this.
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This renames the
@metadata.code.compilation_ordersection to@metadata.code.compilation_priorityand replaces both attributes with a more semantically consistent alternative. Especially, this also removes the previously ill-defined 'hotness' and replaced it by a well-defined 'optimization order' version including suggestions on how this information could be collected.This therefore also addresses issue #7.