Greetings, Please don't top-post on the PG mailing lists, it makes it harder to follow the discussion. * Marco Fortina (marco_fortina@xxxxxxxxxx) wrote: > https://commitfest.postgresql.org/42/3867/ is not exacly what I proposed as new feature to developers. I understood what you were proposing. > If I'm not wrong, almost all main memory areas have a fixed size: > > shared_buffers > effective_cache_size > wal_buffers > > Instead, work_mem is per-process dynamically allocated up to defined size limit. That's not how work_mem works actually. It's a per-node amount and it's not a per-process overall limit, nor is it really a hard limit though some nodes will do their best to respect the amount configured. > What I suggested is to replace work_mem from per-process allocation to global and fixed size allocation (see pga_aggregate_target on Oracle) and shared to worker processes. I understood the suggestion and it's a lot of work for an unclear gain. You noted that having it be pulled from a single area would allow administrators to configure an overall memory usage limit- but that's not the only way to do that and there's an existing effort to do exactly that already underway that's a lot simpler than what you're proposing. While there might be other advantages to having a shared memory segment be used for work_mem, you've not outlined any. > Let's assume the new parameter name is worker_mem_area and this was set to 8GB: with my proposal method each worker process do not use it's own dedicated work_mem but the shared one. I understand your suggestion, but making such a large change just to make it isn't sensible, there should be reasoning behind why that's better than what we're doing already or proposing to do. > In this way each worker is also able to peek free pages from the worker_mem_area if needed. This can be done with the existing approach and doesn't require a shared memory segment for work_mem. We are pretty far from having an actual acceptance system for queries though but I do agree that would be a useful thing to work towards. I don't know that it requires work_mem being in shared memory though. Thanks, Stephen
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