Re: Cost limited statements RFC

On 6/8/13 4:43 PM, Jeff Janes wrote:

> Also, in all the anecdotes I've been hearing about autovacuum causing
> problems from too much IO, in which people can identify the specific
> problem, it has always been the write pressure, not the read, that
> caused the problem. Should the default be to have the read limit be
> inactive and rely on the dirty-limit to do the throttling?

That would be bad, I have to carefully constrain both of them on systems
that are short on I/O throughput. There all sorts of cases where
cleanup of a large and badly cached relation will hit the read limit
right now.

I suspect the reason we don't see as many complaints is that a lot more
systems can handle 7.8MB/s of random reads then there are ones that can
do 3.9MB/s of random writes. If we removed that read limit, a lot more
complaints would start rolling in about the read side.

--
Greg Smith 2ndQuadrant US greg(at)2ndQuadrant(dot)com Baltimore, MD
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