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From: Ross J. Reedstrom <reedstrm@rice.edu>
To: pgsql-performance@postgresql.org
Subject: Re: TCP network cost
Date: Tue, 24 Feb 2009 11:02:01 -0600
Message-ID: <20090224170201.GA25420@cooker> (raw)
In-Reply-To: <27042.1235423820@sss.pgh.pa.us>
References: <1ca1c1410902171013q478f2620n13fcd68cb8b3d911@mail.gmail.com>
	<20090217070403.GB2486@cooker>
	<3FAF940B-9B0B-4DBA-8728-6096022129DF@infogears.com>
	<alpine.DEB.1.10.0902170032440.25606@asgard.lang.hm>
	<20090217070403.GB2486@cooker>
	<3FAF940B-9B0B-4DBA-8728-6096022129DF@infogears.com>
	<20090217200416.GA23707@cooker>
	<87hc2r272g.fsf@oxford.xeocode.com>
	<20090223194212.GA14802@cooker>
	<27042.1235423820@sss.pgh.pa.us>

Excellent. I'll take a look at this and report back here.

Ross


On Mon, Feb 23, 2009 at 04:17:00PM -0500, Tom Lane wrote:
> "Ross J. Reedstrom" <reedstrm@rice.edu> writes:
> > Summary: C client and large-object API python both send bits in
> > reasonable time, but I suspect there's still room for improvement in
> > libpq over TCP: I'm suspicious of the 6x difference. Detailed analysis
> > will probably find it's all down to memory allocation and extra copying
> > of bits around (client side)
> 
> I wonder if the backend isn't contributing to the problem too.  It chops
> its sends up into 8K units, which doesn't seem to create huge overhead
> in my environment but maybe it does in yours.  It'd be interesting to see
> what results you get from the attached quick-and-dirty patch (against
> HEAD, but it should apply back to at least 8.1).
> 
> 			regards, tom lane



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