MapServer performance

[Romolo Manfredini]

Ed wrote:
> Antti -
>
> Even if you don't have control over it, you should still know what it is.
> If you KNOW you're forced to live with a hideously slow disk system, then
> you don't need to waste your time trying to optimize the rest of the
> application.  If you know you have a really high-performing disk system
for
> this application, you can focus on performance improvements in other areas
> and expect them to have some visible effect.
>
I fully agree with Ed.
Antti you should know server performance, also if you have no control on
hardware, if the problem is the hardware then you should suggest to limit
data size to fit the hardware. (maybe reducing the raster size).
15GB Tiff with 1GB Ram and maybe a slow disk subsystem are something that
cannot be improved with application optimization but only with a deep
hardware change. With 1GB and 15GB file you have really no hope to be able
to read from cache.
If you have a shell access on that server try to look to memory and swap
file usage (free), if an application get paged its slowdown is normal.
If you have 10 client connected probably you have 2 or more apache child
serving them, each child allocating memory for file reading and rendering.
When physical memory ends one of the child get paged so on the next request
it we be reloaded and the other paged. This obvioulsy slow down serving
requests.
This explanation is a simplified version of what is going on with paging and
virtual memory but from a practical point of view is not so far from
reality.

Best Regards,
Romolo