Migrates thread local free slot storage from std::list to std::vector.

[birenroy]

std::list is not a great choice for a performance critical utility, as it requires a heap operation on every mutation.

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[repokitteh-read-only]

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Caused by: #44859 was opened by birenroy.

see: more, trace.

[birenroy]

/assign @adisuissa

[adisuissa]

Thanks!
I believe that an std::vector is probably the most optimized data-structure that can be used as a stack to tackle the free_slot_indexes_ accounting (at least from a previous life experience of using different data-structures). WDYT?

[birenroy]

Thanks! I believe that an std::vector is probably the most optimized data-structure that can be used as a stack to tackle the free_slot_indexes_ accounting (at least from a previous life experience of using different data-structures). WDYT?

Sure. The pseudo-random hash set iteration order seemed like a reasonable compromise between the FIFO of the previous version and the LIFO of a vector solution, but it probably doesn't matter.

[adisuissa]

Sure. The pseudo-random hash set iteration order seemed like a reasonable compromise between the FIFO of the previous version and the LIFO of a vector solution, but it probably doesn't matter.

I'm not sure why FIFO was used in the first place, but I don't see a reason why it is required. I've also reviewed #7979 but didn't get any reason why other data types shouldn't be used. LIFO makes more sense IMHO.

[adisuissa]

LGTM, thanks!

[adisuissa]

/assign-from @envoyproxy/senior-maintainers

[repokitteh-read-only]

@envoyproxy/senior-maintainers assignee is @wbpcode

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Caused by: a #44859 (comment) was created by @adisuissa.

see: more, trace.

[ggreenway]

/retest