On Fri, Jun 17, 2016 at 9:30 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Aleksey Demakov <adema...@gmail.com> writes: >> I have some very experimental code to enable dynamic memory allocation >> of shared memory for postgresql backend processes. > > Um ... what's this do that the existing DSM stuff doesn't do? >
It operates over a single large shared memory segment. Within this segment it lets alloc / free small chunks of memory from 16 bytes to 16 kilobytes. Chunks are carved out from fixed-size 32k blocks. Each block is used to allocate chunks of single size class. When a block is full, another block for a given size class is taken from the top shared segment. The goal is to support high levels of concurrency for alloc / free calls. Therefore the allocator is mostly non-blocking. Currently it uses Heller's lazy list algorithm to maintain block lists of a given size class, so it uses slocks once in a while, when a new block is added or removed. If this proves to cause scalability problems the Heller's list might be replaced with Maged Michael's lock-free list to make the whole allocator absolutely lock-free. Additionally it provides epoch-based memory reclamation facility that solves ABA-problem for lock-free algorithms. I am going to implement some lock-free algorithms (extendable hash-tables and probably skip lists) on top of this facility. Regards, Aleksey -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
