On Wed, 15 May 2024 at 13:00, Bruce Momjian <br...@momjian.us> wrote: > > On Tue, May 14, 2024 at 03:39:26PM -0400, Melanie Plageman wrote: > > "Reduce system calls by automatically merging reads up to io_combine_limit" > > Uh, as I understand it, the reduced number of system calls is not the > value of the feature, but rather the ability to request a larger block > from the I/O subsystem. Without it, you have to make a request and wait > for each request to finish. I am open to new wording, but I am not sure > your new wording is accurate.
I think you have the cause and effect backwards. There's no advantage to reading 128KB if you only need 8KB. It's the fact that doing *larger* reads allows *fewer* reads that allows it to be more efficient. There are also the efficiency gains from fadvise POSIX_FADV_WILLNEED. I'm unsure how to jam that into a short sentence. Maybe; "Optimize reading of tables by allowing pages to be prefetched and read in chunks up to io_combine_limit", or a bit more buzzy; "Optimize reading of tables by allowing pages to be prefetched and performing vectored reads in chunks up to io_combine_limit". David
