On Mon, Jul 14, 2025 at 02:34:00PM -0500, Sami Imseih wrote: >> Why do we need three different places for the lock names? Is there a >> reason we can't put it all in shared memory? > > The real reason I felt it was better to keep three separate locations is that > it allows for a clear separation between user-defined tranches registered > during postmaster startup and those registered during a normal backend. The > tranches registered during postmaster are inherited by the backend via > fork() (or EXEC_BACKEND), and therefore, the dshash table will only be used > by a normal backend. > > Since DSM is not available during postmaster, if we were to create a DSA > segment in place, similar to what's done in StatsShmemInit(), we would also > need to ensure that the initial shared memory is sized appropriately. This is > because it would need to be large enough to accommodate all user-defined > tranches registered during postmaster, without having to rely on new > dsm segments. > From my experimentation, this sizing is not as straightforward as simply > calculating # of tranches * size of a tranche entry. > > I still think we should create the dsa during postmaster, as we do with > StatsShmemInit, but it would be better if postmaster keeps its hands off this > dshash and only normal backends can use them.
Ah, I missed the problem with postmaster. Could we have the first backend that needs to access the table be responsible for creating it and populating it with the built-in/requested-at-startup entries? Also, is there any chance that postmaster might need to access the tranche names? -- nathan
