Hi, On 2020-02-14 09:42:40 -0500, Tom Lane wrote: > In the second place, it's ludicrous to expect that the underlying > platform/filesystem can support an infinite number of concurrent > file-extension operations. At some level (e.g. where disk blocks > are handed out, or where a record of the operation is written to > a filesystem journal) it's quite likely that things are bottlenecked > down to *one* such operation at a time per filesystem.
That's probably true to some degree from a theoretical POV, but I think it's so far from where we are at, that it's effectively wrong. I can concurrently extend a few files at close to 10GB/s on a set of fast devices below a *single* filesystem. Whereas postgres bottlenecks far far before this. Given that a lot of today's storage has latencies in the 10-100s of microseconds, a journal flush doesn't necessarily cause that much serialization - and OS journals do group commit like things too. Greetings, Andres Freund
