Tom Lane wrote:
Heikki Linnakangas <[EMAIL PROTECTED]> writes:
imola-336 imola-337 imola-340
writes by checkpoint 38302 30410 39529
writes by bgwriter 350113 2205782 1418672
writes by backends 1834333 265755 787633
writes total 2222748 2501947 2245834
allocations 2683170 2657896 2699974
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It looks like Tom's idea is not a winner; it leads to more writes than
necessary.
The incremental number of writes is not that large; only about 10% more.
The interesting thing is that those "extra" writes must represent
buffers that were re-touched after their usage_count went to zero, but
before they could be recycled by the clock sweep. While you'd certainly
expect some of that, I'm surprised it is as much as 10%. Maybe we need
to play with the buffer allocation strategy some more.
The very small difference in NOTPM among the three runs says that either
this whole area is unimportant, or DBT2 isn't a good test case for it;
or maybe that there's something wrong with the patches?
The small difference in NOTPM is because the I/O still wasn't saturated
even with 10% extra writes.
I ran more tests with a higher number of warehouses, and the extra
writes start to show in the response times. See tests 341-344:
http://community.enterprisedb.com/bgwriter/.
I scheduled a test with the moving average method as well, we'll see how
that fares.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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