Robert Haas <robertmhaas@gmail.com> writes:
> ... How often such a workload actually has to replace a *dirty* clog
> buffer obviously depends on how often you checkpoint, but if you're
> getting ~28k TPS you can completely fill 32 clog buffers (1 million
> transactions) in less than 40 seconds, and you're probably not
> checkpointing nearly that often.
But by the same token, at that kind of transaction rate, no clog page is
actively getting dirtied for more than a couple of seconds. So while it
might get swapped in and out of the SLRU arena pretty often after that,
this scenario seems unconvincing as a source of repeated fsyncs.
Like Andres, I'd want to see a more realistic problem case before
expending a lot of work here.
regards, tom lane