Open jserv opened 10 years ago
lk implements arm-m optimized memcpy and memset routines in git commit https://github.com/travisg/lk/commit/33b94d9b97ef835d68aca2e5edb54f7267c70625
@jserv The profile result:
It looks so weird. Can you explain?
@jserv The implementation is the branch. https://github.com/gapry/f9-kernel/blob/benchmark_memcpy/benchmark/benchmark.c
My approach is that measure the case, alignment and unalignment, five times and take the avg time. Assume my approach is correct, the data imply the conclusion is the unalignment case is better than alignment after the optimized on the stm32F407.
@gapry In order to clarify the performance gain, please compare the optimized memcpy routines with plain byte-oriented C version.
@jserv What does plain byte-oriented mean ?
The simplest and inefficient implementation of memcpy
:
void memcpy(void* src, void* dst, size_t len)
{
char* p = (char*)src;
char* q = (char*)dst;
while(len--) *p++ = *q++;
}
@jserv For now, I use DWT to measure the elapsed clock cycles. You can check the commit: https://github.com/gapry/f9-kernel/commit/33e58dfcb1105140365132269c596763531e9ede
and the completed Implementation: https://github.com/gapry/f9-kernel/blob/benchmark_memcpy/benchmark/benchmark.c
The profile result: unalignment:
alignment:
@gapry I don't think your benchmarking is valid since it doesn't represent the variance. There must be something wrong.
Directory
kernel/lib
contains the implementation ofmemcpy
andmemset
, but it is too generic. We can utilize several ARM Cortex-M3/M4 specific features to optimize: