On Fri, 9 Mar 2007, Jim Nasby wrote:

I'm wondering if pg_bench is a good test of this stuff. ISTM it's unrealistically write-heavy, which is going to tend to not only put a lot of dirty buffers into the pool, but also keep them pinned enough that you can't write them.

Whether it's "unrealistically" write-heavy kind of depends on what your real app is. The standard pgbench is a bit weird because it does so many updates to tiny tables, which adds a level of locking contention that doesn't really reflect many real-world situations. But the no-branch mode (update/select to accounts, insert into history) isn't too dissimilar from some insert-heavy logging applications I've seen.

The main reason I brought this all up was because Itagaki seemed to be using pgbench for some of his performance tests. I just wanted to point out that the LRU background writer specifically tends to be very underutilized when using pgbench.

* Greg Smith [EMAIL PROTECTED] http://www.gregsmith.com Baltimore, MD

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