Re: Bgwriter strategies

Greg Smith wrote:
> On Fri, 6 Jul 2007, Heikki Linnakangas wrote:
> 
>> There's something wrong with that. The number of buffer allocations 
>> shouldn't depend on the bgwriter strategy at all.
> 
> I was seeing a smaller (closer to 5%) increase in buffer allocations 
> switching from no background writer to using the stock one before I did 
> any code tinkering, so it didn't strike me as odd.  I believe it's 
> related to the TPS numbers.  When there are more transactions being 
> executed per unit time, it's more likely the useful blocks will stay in 
> memory because their usage_count is getting tickled faster, and 
> therefore there's less of the most useful blocks being swapped out only 
> to be re-allocated again later.

Did you run the test for a constant number of transactions? If you did, 
the access pattern and the number of allocations should be *exactly* the 
same with 1 client, assuming the initial state and the seed used for the 
random number generator is the same.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com