Increase default maintenance_io_concurrency to 16

2025-03-18 Thread Bruce Momjian
On Tue, Mar 18, 2025 at 04:13:26PM -0400, Andres Freund wrote: > Hi, > > On 2025-03-18 16:08:22 -0400, Bruce Momjian wrote: > > This commit makes our default random_page_cost = 4 out of line with > > these new settings (assumes modern SSD/NAS/SAN hardware) and more out of > > line with reality. >

Re: Increase default maintenance_io_concurrency to 16

2025-03-18 Thread Gregory Smith
On Tue, Mar 18, 2025 at 5:04 PM Andres Freund wrote: > Is that actually a good description of what we assume? I don't know where > that > 90% is coming from? That one's all my fault. It was an attempt to curve-fit backwards why the 4.0 number Tom set with his initial commit worked as well as i

Re: Increase default maintenance_io_concurrency to 16

2025-03-18 Thread Andres Freund
Hi, On 2025-03-18 16:22:45 -0400, Bruce Momjian wrote: > On Tue, Mar 18, 2025 at 04:13:26PM -0400, Andres Freund wrote: > > Hi, > > > > On 2025-03-18 16:08:22 -0400, Bruce Momjian wrote: > > > This commit makes our default random_page_cost = 4 out of line with > > > these new settings (assumes mo

Re: Increase default maintenance_io_concurrency to 16

2025-03-18 Thread Tom Lane
Bruce Momjian writes: >>> https://www.postgresql.org/docs/current/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS >>> >>> Random access to mechanical disk storage is normally much more expensive >>> than four times sequential access. However, a lower default is used >>> (4.0) because the

Re: Increase default maintenance_io_concurrency to 16

2025-03-18 Thread Bruce Momjian
On Tue, Mar 18, 2025 at 05:04:46PM -0400, Andres Freund wrote: > Hi, > > On 2025-03-18 16:35:29 -0400, Bruce Momjian wrote: > > Uh, the random_page_cost = 4 assumes caching, so it is assuming actual > > random I/O to be 40x slower, which I doubt is true for SSDs: > > Uh, huh: > > > > > http

Re: Increase default maintenance_io_concurrency to 16

2025-03-18 Thread Andres Freund
Hi, On 2025-03-18 16:35:29 -0400, Bruce Momjian wrote: > Uh, the random_page_cost = 4 assumes caching, so it is assuming actual > random I/O to be 40x slower, which I doubt is true for SSDs: Uh, huh: > > https://www.postgresql.org/docs/current/runtime-config-query.html#RUNTIME-CONFIG-QUER

Re: Increase default maintenance_io_concurrency to 16

2025-03-18 Thread Bruce Momjian
On Tue, Mar 18, 2025 at 04:27:18PM -0400, Andres Freund wrote: > Hi, > > On 2025-03-18 16:22:45 -0400, Bruce Momjian wrote: > > On Tue, Mar 18, 2025 at 04:13:26PM -0400, Andres Freund wrote: > > > Hi, > > > > > > On 2025-03-18 16:08:22 -0400, Bruce Momjian wrote: > > > > This commit makes our def