Re: [GENERAL] Re : Solaris Performance - Profiling (Solved)

From: mlw <markw(at)mohawksoft(dot)com>
To: Doug McNaught <doug(at)wireboard(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Justin Clift <justin(at)postgresql(dot)org>, Mark kirkwood <markir(at)slingshot(dot)co(dot)nz>, PostgreSQL Hackers Mailing List <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [GENERAL] Re : Solaris Performance - Profiling (Solved)
Date: 2002-04-03 16:24:18
Message-ID: 3CAB2CB2.1745AC2F@mohawksoft.com
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Doug McNaught wrote:
> I think most vendors do a pretty good job. Don't forget, optimizing a
> routine like that depends a lot on the cache size and behavior of the
> CPU and other architecture-dependent stuff.

>> qsort() is a great sort for very random data, when data is mostly in the
>> correct order, it is very bad. Perhaps replacing it with an alternate sort
>> would improve performance in general.

> Actually, the C standard says nothing about what algorithm should be
> used for qsort(); it's simply supposed to be a fast in-memory sort.
> The qsort() name is just a historical artifact.

Perhaps so, but maybe that is the issue with Solaris, it actually may use qsort
algorithm.

I am not too sure how one would optimize the qsort() API on a platform basis.
The sorting algorithm uses a callback function, this precludes any meaningful
optimization. Yea, you can play with memory page sizes, and so on, but you
still have to do a function call for some multiple of the number of elements in
the array.

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