On 2014-08-12 09:42:30 -0700, Sean Chittenden wrote: > One of the patches that I've been sitting on and am derelict in punting > upstream is the attached mmap(2) flags patch for the BSDs. Is there any > chance this can be squeezed in to the PostreSQL 9.4 release? > > The patch is trivial in size and is used to add one flag to mmap(2) calls in > dsm_impl.c. Alan Cox (FreeBSD alc, not Linux) and I went back and forth > regarding PostgreSQL's use of mmap(2) and determined that the following is > correct and will prevent a likely performance regression in PostgreSQL 9.4. > In PostgreSQL 9.3, all mmap(2) calls were called with the flags MAP_ANON | > MAP_SHARED, whereas in PostgreSQL 9.4 this is not the case.
The performancewise important call to mmap will still use that set of flags, no? That's the one backing shared_buffers. The mmap backend for *dynamic* shared memory (aka dsm) is *NOT* supposed to be used on common platforms. Both posix and sysv shared memory will be used before falling back to the mmap() backend. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
