buffer: shrink Slice by moving rare state out of line to save memory - #47101
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botengyao wants to merge 1 commit into
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buffer: shrink Slice by moving rare state out of line to save memory#47101botengyao wants to merge 1 commit into
botengyao wants to merge 1 commit into
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drain_trackers_, account_ and releasor_ are unset on almost every slice but account for 72 of Slice's 112 bytes. Holding them in a lazily allocated Extras takes sizeof(Slice) to 48 bytes, shrinking the 8-slice inline ring every OwnedImpl embeds from 896 to 384 bytes and making a slice move a single pointer move. Slices that do carry an account or a fragment releasor pay one extra small allocation, which is minor next to the >=4kb storage allocation an owned slice already makes. Signed-off-by: Boteng Yao <botengyao@gmail.com>
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drain_trackers_, account_ and releasor_ are unset on almost every slice but account for 72 of Slice's 112 bytes. Holding them in a lazily allocated Extras takes sizeof(Slice) to 48 bytes, shrinking the 8-slice inline ring every OwnedImpl embeds from 896 to 384 bytes and making a slice move a single pointer move. Slices that do carry an account or a fragment releasor pay one extra small allocation, which is minor next to the >=4kb storage allocation an owned slice already makes.
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