Re: Quick idea for reducing VACUUM contention

On Jul 27, 2007, at 1:49 AM, Alvaro Herrera wrote:
> ITAGAKI Takahiro wrote:
>> "Simon Riggs"  wrote:
>>
>>> Read the heap blocks in sequence, but make a conditional lock for
>>> cleanup on each block. If we don't get it, sleep, then try again  
>>> when we
>>> wake up. If we fail the second time, just skip the block completely.
>
> 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
> the locking for those that couldn't be locked the first time around,
> also conditionally.  And when that's all done, a third pass could get
> those blocks that weren't cleaned up in none of the previous passes  
> (and
> this time the lock would not be conditional).

Would that be substantially easier than just creating a bgreader?
--
Jim Nasby                                            jim@nasby.net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)