Re: posix_fadvise v22

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> "Robert Haas" <robertmhaas(at)gmail(dot)com> writes:
>> OK, here's an update of Greg's patch with the runtime configure test
>> ripped out, some minor documentation tweaks, and a few unnecessary
>> whitespace diff hunks quashed. I think this is about ready for
>> committer review.
>
> I've applied most of this, with a couple of notable revisions:
>
> 1. The runtime check on whether posix_fadvise works is really gone.
> We'll see whether we need to put anything back, but I think our first
> try should be under the assumption that it works. (BTW, I was wrong
> in my earlier claim that the buildfarm wouldn't exercise posix_fadvise
> by default --- the patch defaults to io_concurrency = 1 if fadvise
> is available, so it will try to prefetch one page ahead.)
>
> 2. I fixed it so that setting effective_io_concurrency to zero disables
> prefetching altogether; there was no way to do that in the patch as
> submitted.

Hm. the original intent was that effective_io_concurrency 1 meant no
prefetching because there was only one drive.

I wonder if that worked earlier and got lost along the way or if I always had
this wrong.

--
Gregory Stark
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