Re: Bug: Buffer cache is not scan resistant

On Mar 6, 2007, at 12:17 AM, Tom Lane wrote:
> Jim Nasby <decibel@decibel.org> writes:
>> An idea I've been thinking about would be to have the bgwriter or
>> some other background process actually try and keep the free list
>> populated,
>
> The bgwriter already tries to keep pages "just in front" of the clock
> sweep pointer clean.

True, but that still means that each backend has to run the clock- 
sweep. AFAICT that's something that backends will serialize on (due  
to BufFreelistLock), so it would be best to make StrategyGetBuffer as  
fast as possible. It certainly seems like grabbing a buffer off the  
free list is going to be a lot faster than running the clock sweep.  
That's why I think it'd be better to have the bgwriter run the clock  
sweep and put enough buffers on the free list to try and keep up with  
demand.
--
Jim Nasby                                            jim@nasby.net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)