[fpc-devel] Patch, font rendering on Arm-Linux devices.

Daniël Mantione daniel.mantione at freepascal.org
Thu Feb 28 09:16:49 CET 2008

Op Tue, 26 Feb 2008, schreef Luiz Americo Pereira Camara:

> Yury Sidorov wrote:
>> The patch removes packed record for some platforms.
>> IMO packed can be removed for all platforms. It will gain some speed.
> I'd like to understand more this issue.
> Why are non packed records faster?

Cache trashing. One of the most underestimated performance killers in 
modern software.

> The difference occurs at memory allocation or at memory access?

Memory access. What happens is that the non-packed version causes more 
cache misses. A cache miss costs many cycles on a modern cpu, a misaligned 
read just costs an extra memory access (which is fast if cached) on x86, 
and extra load instruction on ARM. This much cheaper than a chache miss.


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