On Wed, Jun 9, 2021 at 9:28 PM Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > > Magnus Hagander <magnus@xxxxxxxxxxxx> writes: > > On Wed, Jun 9, 2021 at 9:15 PM Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > >> Just try to start the server and see if it complains. > > > Well, I have to *stop* the existing one first, most likely, otherwise > > there won't be enough huge pages (or indeed memory) available. > > I'm not following. If you have a production server running, its > pg_shmem_allocations total should already be a pretty good guide > to what you need to configure HugePages for. You need to know to > round that up, of course --- but if you aren't building a lot of > slop into the HugePages configuration anyway, you'll get burned > down the road. I'm talking about the case when you want to *change* the value for shared_buffers (or other parameters that would change the amount of required huge pages), on a system where you're using huge pages. pg_shmem_allocations will tell you what you need with the current value, not what you need with the new value. But yes, you can do some math around it and make a well educated guess. But it would be very convenient to have the system able to do that for you. -- Magnus Hagander Me: https://www.hagander.net/ Work: https://www.redpill-linpro.com/
