Clear ! thanks Laurentz Marc MILLAS Senior Architect +33607850334 www.mokadb.com
On Mon, Nov 17, 2025 at 9:50 PM Laurenz Albe <[email protected]> wrote: > On Mon, 2025-11-17 at 18:25 +0100, Marc Millas wrote: > > Can someone point me to any doc describing why and how much space > postgres uses on the swap of a debian machine ? > > it's an old postgres 10, because it is used by a product for which only > this version is certified. > > (no comment on that, please) > > I'm biting down a comment. > > PostgreSQL itself doesn't use any swap space. > > The kernel can decide to swap out memory used by PostgreSQL. How much > that is depends > on how you configured the Linux kernel and how much memory PostgreSQL > uses. The latter > is mostly determined by "shared_buffers", "work_mem", > "maintenance_work_mem" and > "max_connections". > > On the kernel side, it is mostly the "vm.swappiness" parameter that > determines how > eager the kernel is to swap out memory, even if there is no pressure. For > best > performance, that should happen as little as possible, and the database > should > determine what to keep in memory and what to store on disk. > > One tool you have to prevent shared buffers from being swapped out is to > define enough > Linux hugepages, so that PostgreSQL can allocate shared buffers there. > Linux does not > swap out hugepages. > > You can find the PostgreSQL parameters described in the PostgreSQL > documentation and the > kernel parameters in the kernel documentation. > > Yours, > Laurenz Albe >
