Re: Vacuum rate limit in KBps

On Sun, Jan 15, 2012 at 12:24 AM, Greg Smith <greg(at)2ndquadrant(dot)com> wrote:

> If you then turn that equation around, making the maximum write rate the
> input, for any given cost delay and dirty page cost you can solve for the
> cost limit--the parameter in fictitious units everyone hates.  It works like
> this, with the computation internals logged every time they run for now:
>
> #vacuum_cost_rate_limit = 4000      # maximum write rate in kilobytes/second
> LOG:  cost limit=200 based on rate limit=4000 KB/s delay=20 dirty cost=20

The computation seems to be suffering from some kind of overflow:

cost limit=50 based on rate limit=1000 KB/s delay=20 dirty cost=20
cost limit=100 based on rate limit=2000 KB/s delay=20 dirty cost=20
cost limit=150 based on rate limit=3000 KB/s delay=20 dirty cost=20
cost limit=200 based on rate limit=4000 KB/s delay=20 dirty cost=20
cost limit=250 based on rate limit=5000 KB/s delay=20 dirty cost=20
cost limit=1 based on rate limit=6000 KB/s delay=20 dirty cost=20
cost limit=1 based on rate limit=7000 KB/s delay=20 dirty cost=20
cost limit=1 based on rate limit=8000 KB/s delay=20 dirty cost=20

Cheers,

Jeff