From: Martijn van Oosterhout <kleptog@svana.org>
To: Gregory Stark <stark@enterprisedb.com>
Cc: Bruce Momjian <bruce@momjian.us>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Commitfest patches
Date: Fri, 28 Mar 2008 19:48:47 +0100
Message-ID: <20080328184847.GE9150@svana.org> (raw)
In-Reply-To: <87r6duycpl.fsf@oxford.xeocode.com>
References: <200803281545.m2SFjpL18390@momjian.us>
<87r6duycpl.fsf@oxford.xeocode.com>
On Fri, Mar 28, 2008 at 05:34:30PM +0000, Gregory Stark wrote:
> But what I really need is someone to read the patch and say "looks good" or
> point out things they don't like. In particular, what I really, really want is
> some guidance on the singular key question I asked.
I was going to write all sorts of stuff, till I noticed Heikki said
basically everything I was going to say:
- I think normal index scans could benefit from this (it was measurable
when I was playing with AIO in postgres a few years back).
- The integration with the bitmap scan is good, neat even
- I think the number of preread_count is far too small, given you get a
benefit even if you only have one spindle.
- I don't understand the ramp-up method either.
People spend a lot of time worrying about hundreds of posix_fadvise()
calls but you don't need anywhere near that much to be effective. With
AIO I limited the number of outstanding requests to a dozen and it was
still useful. You lose nothing by capping the number of requests at any
point.
> I want to know if we're interested in the more invasive patch restructuring
> the buffer manager. My feeling is that we probably are eventually. But I
> wonder if people wouldn't feel more comfortable taking baby steps at first
> which will have less impact in cases where it's not being heavily used.
I think the way it is now is neat and simple and enough for now.
Have a nice day,
--
Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/> Please line up in a tree and maintain the heap invariant while
> boarding. Thank you for flying nlogn airlines.
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To: pgsql-hackers@postgresql.org
Cc: kleptog@svana.org, stark@enterprisedb.com, bruce@momjian.us
Subject: Re: Commitfest patches
In-Reply-To: <20080328184847.GE9150@svana.org>
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