Date: Tue, 25 Apr 2006 08:38:55 -0500 From: Derek Ragona <derek@computinginnovations.com> To: Bill Moran <wmoran@collaborativefusion.com> Cc: freebsd-questions@freebsd.org Subject: Re: Purchasing the correct hardware: dual-core intel? Big cache? Message-ID: <6.0.0.22.2.20060425083303.0293a8a8@mail.computinginnovations.com> In-Reply-To: <20060425092526.6fe5efa6.wmoran@collaborativefusion.com> References: <20060424154617.9dc28c94.wmoran@potentialtech.com> <6.0.0.22.2.20060424175443.02927f48@mail.computinginnovations.com> <20060425084752.2453c0f1.wmoran@collaborativefusion.com> <6.0.0.22.2.20060425075227.028aea10@mail.computinginnovations.com> <20060425092526.6fe5efa6.wmoran@collaborativefusion.com>
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Bill,
Never assume . . .
Depending on where you got the PostgreSQL, was it in binary form or
source. Most binarys are NOT optimized for higher end, more current
processors, rather they are optimized for the most common family of CPU's.
But if your database application is really CPU bound, I would look at the
data model and how your application is accessing and using the
data. RDBMS's can be very effiicent, or terribly inefficient. In the
worst case you can cause an RDBMS to serially go through every record
searching for data or doing a calculation.
While a bigger cache may help, as may dual core CPU's, or faster CPU's. In
the end, you may only see marginal improvement if the application or
database is really where you need to tune things.
-Derek
At 08:25 AM 4/25/2006, Bill Moran wrote:
>On Tue, 25 Apr 2006 07:56:03 -0500
>Derek Ragona <derek@computinginnovations.com> wrote:
>
> > Yes, dual core is on average 20% faster than hyperthreaded CPU's. But
> that
> > is general benchmark. The range of performance difference is 10% - 30%
> > depending on the application mix.
>
>Thanks.
>
> > If you use well optimized applications, you see the larger performance
> > gain. Poor optimization causes a CPU to chug along, flushing the CPU
> cache
> > often, and slowing things down considerably.
>
>I know. That's why I'm so desperately trying to find a way to determine
>how often the cache is being invalidated - so I can determine whether
>larger cache sizes (such as 8M) are worthwhile.
>
>The database server is PostgreSQL. If we find optimization problems
>with it, we'll definitely work with the PostgreSQL folks to get those
>problems addressed, but I'm not expecting a lot of poorly-written code
>in something as mature as PostgreSQL. So, making a (reasonable)
>assumption that PostgreSQL is well-optimized, I need a way to tell if
>adding another 6M of cache will improve performance, _before_ we pay
>for it.
>
>That's my question.
>
>--
>Bill Moran
>Collaborative Fusion Inc.
>
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