Hi, On 2023-02-17 09:52:01 -0800, Andres Freund wrote: > On 2023-02-17 17:26:20 +1300, David Rowley wrote: > Random note: > > I wonder if we should having a bitmap (in an int) in front of aset's > freelist. In a lot of cases we incur plenty cache misses, just to find the > freelist bucket empty.
Two somewhat related thoughts: 1) We should move AllocBlockData->freeptr into AllocSetContext. It's only ever used for the block at the head of ->blocks. We completely unnecessarily incur more cache line misses due to this (and waste a tiny bit of space). 2) We should introduce an API mcxt.c API to perform allocations that the caller promises not to individually free. We've talked a bunch about introducing a bump allocator memory context, but that requires using dedicated memory contexts, which incurs noticable space overhead, whereas just having a separate function call for the existing memory contexts doesn't have that issue. For aset.c we should just allocate from set->freeptr, without going through the freelist. Obviously we'd not round up to a power of 2. And likely, at least outside of assert builds, we should not have a chunk header. Greetings, Andres Freund
