Re: lazy vxid locks, v1

From: Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>
To: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: robertmhaas(at)gmail(dot)com, pgsql-hackers(at)postgresql(dot)org
Subject: Re: lazy vxid locks, v1
Date: 2011-06-13 12:46:51
Message-ID: 4DF606BB.5060602@kaltenbrunner.cc
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On 06/13/2011 02:29 PM, Kevin Grittner wrote:
> Stefan Kaltenbrunner wrote:
>
>> on that particular 40cores/80 threads box:
>
>> unpatched:
>
>> c40: tps = 107689.945323 (including connections establishing)
>> c80: tps = 101885.549081 (including connections establishing)
>
>> fast locks:
>
>> c40: tps = 215807.263233 (including connections establishing)
>> c80: tps = 118266.615543 (including connections establishing)
>
>> fast locks + lazy vxid:
>
>> c40: tps = 223308.779212 (including connections establishing)
>> c80: tps = 65738.046558 (including connections establishing)
>
> Is there any way to disable the HT (or whatever technology attempts
> to make each core look like 2)? In my benchmarking that has kept
> performance from tanking as badly when a large number of processes
> are contending for CPU.

I can do that tomorrow, but I have now done a fair amount of
benchmarking on that box using various tests and for CPU intense
workloads(various math stuff, parallel compiles of the linux kernel,
some inhouse stuff, and some other database) I usually get a 60-70x
speedup over just using a single core and most recent CPUs (this one is
actually a brand new Westmere-EX) showed pretty good scaling with
HT/threading.
I'm actually pretty sure that at leas in some benchmarks it was not HT
that was the real problem but rather our general inability to scale much
beyond 10-12 cores for reads and even worse for writes (due to WAL
contention).

Stefan

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