On 22/02/2024 01:03, Thomas Munro wrote:
On Thu, Feb 22, 2024 at 10:30 AM Thomas Munro <thomas.mu...@gmail.com> wrote:
collisions arbitrarily far apart (just decide how many bits to use).

. o O ( Perhaps if you also allocated slots using a FIFO freelist,
instead of the current linear search for the first free slot, you
could maximise the time before a slot is reused, improving the
collision-avoiding power of a generation scheme? )

We could also enlarge dsm_handle from 32-bits to 64-bits, if we're worried about collisions.

I actually experimented with something like that too: I encoded the "is this in main region" in one of the high bits and let the implementation use the low bits. One small issue with that is that we have a few places that pass a DSM handle as the 'bgw_main' argument when launching a worker process, and on 32-bit platforms that would not be wide enough. Those could be changed to use the wider 'bgw_extra' field instead, though.

--
Heikki Linnakangas
Neon (https://neon.tech)



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