On 10.10.12 14:40, dhkblas...@zeelandnet.nl wrote: > One more question, when using packed records, is there anything to say > about performance? Are there some tests anywhere that show how the > performance is impacted?
This highly depends on the architecture/processor. Many architectures (like older ARMs) can not handle unaligned access at all. Such an access would create an exception, which has to be handled by the system (Linux provides the capability to emulate these faults, but at a VERY high performance cost). Thats why fpc emits byte loads for halfword and word loads on packed records. But for a words these will also take about 7-15 cycles, depending in the compiler version and core used. Newer ARM implementations can handle unaligned access, but only under some performance penalty. x86 can handle unaligned access, but most implementations (I think current atoms and via nano are an exception) will suffer a rather high performance penalty. If you only use packed records to get your data from and to disk/network you'll not see much of a difference, but you should avoid using a packed record inside something which is performance sensitive. Nico _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
