Re: [dpdk-dev] [PATCH v4 2/3] test/distributor: replace sync builtins with atomic builtins

["Hunt, David" <david.hunt@intel.com>]

Hi Phil,

On 8/4/2019 4:02 AM, Phil Yang wrote:
> '__sync' built-in functions are deprecated, should use the '__atomic'
> built-in instead. the sync built-in functions are full barriers, while
> atomic built-in functions offer less restrictive one-way barriers,
> which help performance.
>
> Here is the example test result on TX2:
> sudo ./arm64-armv8a-linuxapp-gcc/app/test -l 112-139 \
> -n 4 --socket-mem=1024,1024 -- -i
> RTE>>distributor_perf_autotest
>
> *** distributor_perf_autotest without this patch ***
> ==== Cache line switch test ===
> Time for 33554432 iterations = 1519202730 ticks
> Ticks per iteration = 45
>
> *** distributor_perf_autotest with this patch ***
> ==== Cache line switch test ===
> Time for 33554432 iterations = 1251715496 ticks
> Ticks per iteration = 37
>
> Less ticks needed for the cache line switch test. It got 17% of
> performance improvement.


I'm seeing about an 8% performance degradation on my platform for the 
cache line switch test with the patch, however the single mode and burst 
mode tests area showing no difference, which are the more important 
tests. What kind of differences are you seeing in the single/burst mode 
tests?

Rgds,
Dave.


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