Re: Free WAL caches on switching segments

Tom Lane wrote:
> Mark Kirkwood <markir@paradise.net.nz> writes:
> > Thinking about this, presumably any write intensive, multi-user
> > benchmark would seem to be suitable, so would something like OSDL's
> > DBT-2 actually be better to try?
>
> I'm certainly not wedded to pgbench, give it a try.
>
> BTW, I forgot to mention that it would be useful to try different
> wal_sync_methods along with this.  The reason why it seems unlikely
> the patch is useful on Linux is that the sync methods that use O_DIRECT
> probably dominate using the patch anyway.  There may or may not be
> a similar dependence on sync method on other kernels ...

I am thinking the only way to test this would be to do one heavy update
session to generate a lot of WAL traffic, and another session that is
doing a sequential scan on a table that fills most of the cache.  It
isn't an easy test to make, which was why I was thinking we just add the
patch, but the community disagrees.

--
  Bruce Momjian   http://candle.pha.pa.us
  SRA OSS, Inc.   http://www.sraoss.com

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