Re: Quick idea for reducing VACUUM contention

On Jul 30, 2007, at 1:47 PM, Alvaro Herrera wrote:
> Jim Nasby wrote:
>> On Jul 27, 2007, at 1:49 AM, Alvaro Herrera wrote:
>>> ITAGAKI Takahiro wrote:
>>> It would be cool if we could do something like sweep a range of
>>> pages,
>>> initiate IO for those that are not in shared buffers, and while
>>> that is
>>> running, lock and clean up the ones that are in shared buffers,
>>> skipping
>>> those that are not lockable right away; when that's done, go back to
>>> those buffers that were gotten from I/O and clean those up. And
>>> retry
>>
>> Would that be substantially easier than just creating a bgreader?
>
> I'm not sure about easier, but I'm not sure that the bgreader can
> do the
> same job. ISTM that the bgreader would be mostly in charge of reading
> in advance of backends, whereas what I'm proposing is mostly about
> finding the best spot for locking. It might turn out to be more
> trouble
> than it's worth though, for sure. And in any case I'm not in a
> hurry to
> implement it.

I was referring specifically to the "read in what's not already in
shared buffers" part of Itagaki-san's message... that seems to be
something best suited for a bgreader.
--
Decibel!, aka Jim Nasby decibel(at)decibel(dot)org
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)