Re: Load distributed checkpoint

Bruce Momjian <bruce(at)momjian(dot)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 ...

regards, tom lane