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Re: Checkpointer split has broken things dramatically (was Re: DELETE vs TRUNCATE explanation)

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Greg Smith <greg@2ndQuadrant.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Jeff Janes <jeff.janes@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Daniel Farina <daniel@heroku.com>, Craig Ringer <ringerc@ringerc.id.au>, "Harold A. Giménez" <harold.gimenez@gmail.com>
Date: 2012-07-18T05:56:05Z
Lists: pgsql-hackers, pgsql-performance 
Greg Smith <greg@2ndQuadrant.com> writes:
> On 07/17/2012 06:56 PM, Tom Lane wrote:
>> Furthermore, I would say that any performance testing done since then,
>> if it wasn't looking at purely read-only scenarios, isn't worth the
>> electrons it's written on.  In particular, any performance gain that
>> anybody might have attributed to the checkpointer splitup is very
>> probably hogwash.

> There hasn't been any performance testing that suggested the 
> checkpointer splitup was justified.  The stuff I did showed it being 
> flat out negative for a subset of pgbench oriented cases, which didn't 
> seem real-world enough to disprove it as the right thing to do though.

Just to clarify, I'm not saying that this means we should revert the
checkpointer split.  What I *am* worried about is that we may have been
hacking other things on the basis of faulty performance tests.

			regards, tom lane

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Scan the buffer pool just once, not once per fork, during relation drop.