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From: Tom Lane <[email protected]>
To: Felix Geisendörfer <[email protected]>
Cc: [email protected]
Subject: Re: 10x faster sort performance on Skylake CPU vs Ivy Bridge
Date: Fri, 25 Aug 2017 11:07:21 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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=?utf-8?Q?Felix_Geisend=C3=B6rfer?= <[email protected]> writes:
> I recently came across a performance difference between two machines that surprised me:
> ...
> As you can see, Machine A spends 5889ms on the Sort Node vs 609ms on Machine B when looking at the "Exclusive" time with explain.depesz.com [3][4]. I.e. Machine B is ~10x faster at sorting than Machine B (for this particular query).

I doubt this is a hardware issue, it's more likely that you're comparing
apples and oranges.  The first theory that springs to mind is that the
sort keys are strings and you're using C locale on the faster machine but
some non-C locale on the slower.  strcoll() is pretty darn expensive
compared to strcmp() :-(

			regards, tom lane


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