Hello,
The following things made me think that rte_memcpy() is more optimized
than memcpy():
1. dpdk documentation recommends to use rte_memcpy() instead of memcpy():
https://doc.dpdk.org/guides/prog_guide/writing_efficient_code.html
2. Here some benchmarks are available:
https://software.intel.com/content/www/us/en/develop/articles/performance-optimization-of-memcpy-in-dpdk.html
3. rte_memcpy() has __attribute__((always_inline)) associated with it,
so compiler also tries to inline it.
Using rte_memcpy() everywhere ensures consistency in code-base.
Here are the results of the performance number measurement using "perf":
rte_memcpy()
Performance counter stats
1.573864 task-clock (msec) # 0.898 CPUs
utilized
0 context-switches # 0.000 K/sec
0 cpu-migrations # 0.000 K/sec
342 page-faults # 0.217 M/sec
5,483,016 cycles # 3.484 GHz
5,554,017 instructions # 1.01 insn per
cycle
1,114,593 branches # 708.189 M/sec
33,796 branch-misses # 3.03% of all
branches
1,369,247 L1-dcache-loads # 869.991 M/sec
<not counted> L1-dcache-load-misses
(0.00%)
<not counted> LLC-loads
(0.00%)
<not counted> LLC-load-misses
(0.00%)
0.001753373 seconds time elapsed
memcpy()
Performance counter stats
1.631135 task-clock (msec) # 0.902 CPUs
utilized
0 context-switches # 0.000 K/sec
0 cpu-migrations # 0.000 K/sec
342 page-faults # 0.210 M/sec
5,676,549 cycles # 3.480 GHz
(73.99%)
5,739,593 instructions # 1.01 insn per
cycle
1,141,121 branches # 699.587 M/sec
34,553 branch-misses # 3.03% of all
branches
1,417,494 L1-dcache-loads # 869.023 M/sec
67,312 L1-dcache-load-misses # 4.75% of all
L1-dcache hits (26.01%)
<not counted> LLC-loads
(0.00%)
<not counted> LLC-load-misses
(0.00%)
0.001808500 seconds time elapsed
On Thu, Jul 23, 2020 at 8:47 PM Stephen Hemminger
<step...@networkplumber.org> wrote:
>
> On Thu, 23 Jul 2020 12:02:40 +0500
> Sarosh Arif <sarosh.a...@emumba.com> wrote:
>
> > Since rte_memcpy is more optimized it should be used instead of memcpy
> >
> > Signed-off-by: Sarosh Arif <sarosh.a...@emumba.com>
>
> Really did you measure this.
> For fixed size structures, compiler can inline memcpy small set of
> instructions.
