Re: Cost limited statements RFC

On 6/7/13 12:42 PM, Robert Haas wrote:
> GUCs in terms of units that are meaningful to the user.  One could
> have something like io_rate_limit (measured in MB/s),
> io_read_multiplier = 1.0, io_dirty_multiplier = 1.0, and I think that
> would be reasonably clear.

There's one other way to frame this:

io_read_limit = 7.8MB/s # Maximum read rate
io_dirty_multiplier = 2.0  # How expensive writes are considered 
relative to reads

That still gives all of the behavior I'd like to preserve, as well as 
not changing the default I/O pattern.  I don't think it's too 
complicated to ask people to grapple with that pair.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com