Re: Load distributed checkpoint

Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > Jim C. Nasby wrote:
> >> What about the mmap/msync(?)/munmap idea someone mentioned?
> 
> > I see that as similar to using O_DIRECT during checkpoint, which had
> > poor performance.
> 
> That's a complete nonstarter on portability grounds, even if msync gave
> us the desired semantics, which it doesn't.  It's no better than fsync
> for our purposes.
> 
> To my mind the problem with fsync is not that it gives us too little
> control but that it gives too much: we have to specify a particular
> order of writing out files.  What we'd really like is a version of
> sync(2) that tells us when it's done but doesn't constrain the I/O
> scheduler's choices at all.  Unfortunately there's no such API ...

Yea, we used to use sync() but that did all files, not just the
PostgreSQL ones.

--  Bruce Momjian   bruce@momjian.us EnterpriseDB    http://www.enterprisedb.com
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