Simon Riggs wrote:
On Mon, 2007-03-05 at 14:41 -0500, Tom Lane wrote:
"Simon Riggs" <[EMAIL PROTECTED]> writes:
Itakgaki-san and I were discussing in January the idea of cache-looping,
whereby a process begins to reuse its own buffers in a ring of ~32
buffers. When we cycle back round, if usage_count==1 then we assume that
we can reuse that buffer. This avoids cache swamping for read and write
workloads, plus avoids too-frequent WAL writing for VACUUM.
This would maintain the beneficial behaviour for OLTP,
Justify that claim.  It sounds to me like this would act very nearly the
same as having shared_buffers == 32 ...

Sure. We wouldn't set the hint for IndexScans or Inserts, only for
SeqScans, VACUUM and COPY.

So OLTP-only workloads would be entirely unaffected. In the presence of
a mixed workload the scan tasks would have only a limited effect on the
cache, maintaining performance for the response time critical tasks. So
its an OLTP benefit because of cache protection and WAL-flush reduction
during VACUUM.

As we've seen, the scan tasks look like they'll go faster with this.

But it would break the idea of letting a second seqscan follow in the
first's hot cache trail, no?

greetings, Florian Pflug

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