On Sun, Jan 5, 2014 at 1:28 PM, knizhnik <knizh...@garret.ru> wrote: > From my point of view it is not a big problem that it is not possible to > place LWLock in DSM. > I can allocate LWLocks in standard way - using RequestAddinLWLocks and use > them for synchronization.
Sure, well, that works fine if you're being loaded from shared_preload_libraries. If you want to be able to load the extension after startup time, though, it's no good. > And what I still do not completely understand - how DSM enforces that > segment created by one PosatgreSQL process will be mapped to the same > virtual memory address in all other PostgreSQL processes. It doesn't. One process calls dsm_create() to create a shared memory segment. Other processes call dsm_attach() to attach it. There's no guarantee that they'll map it at the same address; they'll just map it somewhere. > Or may be DSM doesn't guarantee than DSM segment is mapped to the same > address in all processes? > In this case it significantly complicates DSM usage: it will not be possible > to use direct pointers. Yeah, that's where we're at. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
