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Re: profile-guided opt. w/ GCC

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Peter Eisentraut <peter_e(at)gmx(dot)net>
Cc: Neil Conway <neilc(at)samurai(dot)com>,pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: profile-guided opt. w/ GCC
Date: 2004-09-30 14:23:05
Message-ID: 16093.1096554185@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> Neil Conway wrote:
>> The patch adds a new make target ("profile-opt") that does the PGO
>> steps outlined above -- the "representative input data" is the
>> regression tests running in serial mode. I haven't run any benchmarks
>> yet (if someone wants to try that, I'd be very curious to see the
>> results).

> I doubt that the regression tests are anywhere near representative input 
> data.  They run a proportion of borderline and error cases that is much 
> higher than I would expect in normal use.

Also, the serial regression tests provide absolutely 0 exercise for any
of the code paths associated with concurrent behavior.  At minimum I'd
suggest using the parallel tests instead.

It might be interesting to compare the results from PGO using the
regression tests to PGO using pgbench.  pgbench probably goes overboard
in the other direction of not exercising enough stuff, but it would give
us some kind of data point about the consequences of different profiling
loads.

			regards, tom lane

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