size_t QuickVec and Appropriate BlockData Fields - #1402
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tobil4sk
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Merging since this new CI failure is also happening on master. |
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"size_t QuickVec and Appropriate BlockData Fields" (HaxeFoundation#1402) made BlockDataInfo's mUsedRows and mFraggedRows uint8_t. A block's row counts run up to IMMIX_USEFUL_LINES, which is 254 with the default 32k blocks but 508 with HXCPP_GC_BIG_BLOCKS, whose 64k blocks have 512 lines of 128 bytes. There the counts wrap: makeFull() and a full countRows() store 508 as 252, reclaim() stores IMMIX_USEFUL_LINES - freeLines the same way, countRows() never sees a full block as full, and a block with 256 used rows reads as empty. The rows-in-use total the collector sums after each collection, and with it the working-memory target it sets, comes out far below the live heap, so allocation runs a collection almost every time it asks for a new block. A program that builds 6M small live objects and then allocates 30M short-lived ones takes about 0.4s with default blocks, and 15 to 20s with big blocks (60 to 70s of CPU across the marking threads). With this change it takes about 0.4s with either. mUsedRows and mFraggedRows are uint16_t again, as is the allocator's pointer to the fragmented-row count, and static_asserts check that both can hold IMMIX_USEFUL_LINES, so narrowing them again fails the build. The byte counts were fine: 508 lines of 128 bytes is 65024, which a uint16_t holds. (cherry picked from commit 50f1f61)
dimensionscape
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HaxeFoundation#1402 made BlockDataInfo's mUsedRows and mFraggedRows uint8_t, which fits the default 32k blocks (254 usable lines) but not big blocks (508). With HXCPP_GC_BIG_BLOCKS the counts wrap, the GC underestimates the live heap, and it ends up collecting on almost every new block. Use uint16_t for both (and for the allocator's mFraggedRows pointer), with static_asserts so they can't drop below IMMIX_USEFUL_LINES again.
dimensionscape
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Oct 2, 2026
HaxeFoundation#1402 made BlockDataInfo's mUsedRows and mFraggedRows uint8_t, which fits the default 32k blocks (254 usable lines) but not big blocks (508). With HXCPP_GC_BIG_BLOCKS the counts wrap, the GC underestimates the live heap, and it ends up collecting on almost every new block. Use uint16_t for both (and for the allocator's mFraggedRows pointer), with static_asserts so they can't drop below IMMIX_USEFUL_LINES again. (cherry picked from commit 71bf02d)
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This updates
QuickVecto be based onsize_tand updates the fields in theBlockDataclass to be "properly" sized. I didn't go with size_t for many of those fields as they can be much narrower. E.g. each block only has 256 lines (two of which are used for block metadata) and each line is 128 bytes long, souint8_tanduint16_tare natural fits for this.