| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, digoal zhou <digoal(dot)zhou(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Let PostgreSQL's On Schedule checkpoint write buffer smooth spread cycle by tuning IsCheckpointOnSchedule? |
| Date: | 2015-07-05 15:09:25 |
| Message-ID: | 20150705150925.GG24494@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
On 2015-07-05 11:05:28 -0400, Robert Haas wrote:
> More broadly, I don't really know how to test this patch and show when
> it helps and when it hurts. And I think we need that, rather than
> just a theoretical analysis, to tune the behavior. Heikki, can you
> describe what you think a good test setup would be? Like, what
> workload should we run, and what measurements should we gather to see
> what the patch is doing that is good or bad?
I think a good start would be to graph the writeout rate over several
checkpoints. It'd be cool if there were a better way, but it's probably
easiest to just graph the number of bytes written (using iostat) and the
number of dirty bytes in the kernel. That'll unfortunately include WAL,
but I can't immediately see how to avoid that.
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