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Re: spinlocks on HP-UX

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: spinlocks on HP-UX
Date: 2011-08-29 18:32:49
Message-ID: CA+Tgmoaxzc_qFv6L04wM0wdkGVUkzuNT0pD-dGp-qznqZGO4Zw@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Mon, Aug 29, 2011 at 2:15 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> These tests were run on a 32-CPU Opteron machine (Sun Fire X4600 M2,
> 8 quad-core sockets).  Test conditions the same as my IA64 set, except
> for the OS and the -j switches:
>
> Stock git head:
>
> pgbench -c 1 -j 1 -S -T 300 bench       tps = 9515.435401 (including ...
> pgbench -c 32 -j 16 -S -T 300 bench     tps = 227349.424654 (including ...
>
> These tests were run on a 32-processor PPC64 machine (IBM 8406-71Y,
> POWER7 architecture; I think it might be 16 cores with hyperthreading,
> not sure).  The machine has "only" 6GB of RAM so I set shared_buffers to
> 4GB, other test conditions the same:
>
> Stock git head:
>
> pgbench -c 1 -j 1 -S -T 300 bench       tps = 8746.076443 (including ...
> pgbench -c 32 -j 16 -S -T 300 bench     tps = 126822.857978 (including ...

Stepping beyond the immediate issue of whether we want an unlocked
test in there or not (and I agree that based on these numbers we
don't), there's a clear and puzzling difference between those sets of
numbers.  The Opteron test is showing 32 clients getting about 23.9
times the throughput of a single client, which is not exactly linear
but is at least respectable, whereas the PPC64 test is showing 32
clients getting just 14.5 times the throughput of a single client,
which is pretty significantly less good.  Moreover, cranking it up to
64 clients is squeezing a significant amount of additional work out on
Opteron, but not on PPC64.  The HP-UX/Itanium numbers in my OP give a
ratio of 17.3x - a little better than your PPC64 numbers, but
certainly not great.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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