| From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)heroku(dot)com> |
| Cc: | Amit Langote <amitlangote09(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: XLogFlush invoked about twice as much after 9.2 group commit enhancement |
| Date: | 2013-05-08 16:27:33 |
| Message-ID: | CAMkU=1y0+GYtkXqr5VbqwCxqBaNt99tfRYXOazTsBis418iVNQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, May 7, 2013 at 9:23 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> On Tue, May 7, 2013 at 12:48 PM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
> > Anyway, I don't see this behavior change when turning on wal_debug and
> > looking in the logfiles for 'xlog flush request' messages.
>
> That could have everything to do with the hardware you're using. In
> general, the higher the cost of an fsync, the more useful it is to
> amortize that cost among concurrently committing transactions.
>
True, but that is going to happen with a proportional increase in
throughput, which he reported not seeing. At least originally. I'm not
sure what to think now.
Cheers,
Jeff
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