runtime (gc): bundle small allocations together #992
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aykevl
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Apr 6, 2020
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I am somewhat cautious with this change. The benefit here is not nearly as obvious as with code size decreases or correctness fixes. In fact, a quick test with Therefore, I think the improvement should be measured in a real-world piece of code (such as the mqtt code we've been using for testing so far). How much is heap usage reduced? Is that reduction worth the cost, especially for small systems with little RAM (that would potentially benefit the most)? |
This reduces the overhead of small allocations. Previously a pointer sized allocation would take up an entire block - leaving 3 pointer-widths of wasted space. Small allocations are now bundled together, and are treated as a single object for garbage-collection purposes. These could be tracked seperately, but not without paying for space to store additional garbage collector metadata.
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I think this can be done more efficiently with #1181 if we decide we want this |
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This reduces the overhead of small allocations. Previously a pointer sized allocation would take up an entire block - leaving 3 pointer-widths of wasted space. Small allocations are now bundled together, and are treated as a single object for garbage-collection purposes. These could be tracked separately, but not without paying for space to store additional garbage collector metadata.
Most tests in
testdatacallsmallAllocat some point.