Hacker News Reader

See Bonwick & Adams, "Magazines and Vmem: extending the slab allocator to many CPUs and arbitrary resources" from 2001: https://www.usenix.org/conference/2001-usenix-annual-technic...

The most general allocator interface described, vmem_xalloc(), includes a "phase" parameter (their name for "align at offset"), as well as a "nocross" parameter (in case you want your oddly-aligned object to not cross a page boundary).

View on HN

Hmm, paying a whole extra register for `nocross` is pretty expensive ... though representing it as a logarithm means it only needs to represent 62 values (2^1 is meaningless for both 1-byte and 2-byte allocations, 2^64 cannot be crossed regardless), which is 6 bits, so we could stuff it in the flags or even the high bits of the alignment on 32-bit-or-larger platforms. That seems like the way to do it ... unless it is instead specified as part of the allocator itself.

Anyway, added that and other flags in that paper to my central list at https://gist.github.com/o11c/6b08643335388bbab0228db763f9921...

not sure if it was a factor in the API design, but SPARC's fixed-size register windows give you space for 8 parameters. Perhaps it's just coincidence, but vmem_xalloc() takes exactly 8 parameters!

Reply on news.ycombinator.com