The following documentation comment has been logged on the website: Page: https://www.postgresql.org/docs/16/kernel-resources.html Description:
PostgreSQL documentation point to kernel documentation for info about vm.overcommit_ratio. But kernel documentation slightly incorrect, so may be write slightly more here. Kernel documentation said: The total address space commit for the system is not permitted to exceed swap + a configurable amount (default is 50%) of physical RAM. Where 50% is the default for vm.overcommit_ratio. But really not "physical RAM" is taken in case when using hugepage memory (common practice for postgresql). For instance I have 1TiB physical memory and 800 GiB is reserved for hugepage (1GiB pagesize). "50% of physical RAM" will be not 500 GiB, as expected, but roughly 100GiB=0.5*(1000-800), and commit limit will be 100GiB+swap size.
