Re: Experimental patch for inter-page delay in VACUUM

Tom Lane wrote:
> Jan Wieck <JanWieck@Yahoo.com> writes:
> > That is part of the idea. The whole idea is to issue "physical" writes 
> > at a fairly steady rate without increasing the number of them 
> > substantial or interfering with the drives opinion about their order too 
> > much. I think O_SYNC for random access can be in conflict with write 
> > reordering.
> 
> Good point.  But if we issue lots of writes without fsync then we still
> have the problem of a write storm when the fsync finally occurs, while
> if we fsync too often then we constrain the write order too much.  There
> will need to be some tuning here.

I know the BSD's have trickle sync --- if we write the dirty buffers to
kernel buffers many seconds before our checkpoint, the kernel might
right them to disk for use and sync() will not need to do it.

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