test/ring: reduce duration of performance tests

test/ring: reduce duration of performance tests

When testing ring performance in the case that multiple lcores are mapped
to the same physical core, e.g. --lcores '(0-3)@10', it takes a very long
time to wait for the "enqueue_dequeue_bulk_helper" to finish.
This is because too much iteration numbers and extremely low efficiency
for enqueue and dequeue with this kind of core mapping. Following are the
test results to show the above phenomenon:

x86-Intel(R) Xeon(R) Gold 6240:
$sudo ./app/test/dpdk-test --lcores '(0-1)@25'
Testing using two hyperthreads(bulk (size: 8):)
iter_shift:         3     5     7     9     11     13    *15     17     19     21      23
run time:           7s    7s    7s    8s    9s     16s    47s    170s   660s   >0.5h   >1h
legacy APIs: SP/SC: 37    11    6     40525 40525  40209  40367  40407  40541  NoData  NoData
legacy APIs: MP/MC: 56    14    11    50657 40526  40526  40526  40625  40585  NoData  NoData

aarch64-n1sdp:
$sudo ./app/test/dpdk-test --lcore '(0-1)@1'
Testing using two hyperthreads(bulk (size: 8):)
iter_shift:         3     5     7     9     11     13    *15     17     19     21      23
run time:           8s    8s    8s    9s    9s     14s    34s    111s   418s   25min   >1h
legacy APIs: SP/SC: 0.4   0.2   0.1   488   488    488    488    488    489    489     NoData
legacy APIs: MP/MC: 0.4   0.3   0.2   488   488    488    488    490    489    489     NoData

As the number of iterations increases, so does the time which is required
to run the program. Currently (iter_shift = 23), it will take more than
1 hour to wait for the test to finish. To fix this, the "iter_shift" should
decrease and ensure enough iterations to keep the test data stable.
In order to achieve this, we also test with "-l" EAL argument:

x86-Intel(R) Xeon(R) Gold 6240:
$sudo ./app/test/dpdk-test -l 25-26
Testing using two NUMA nodes(bulk (size: 8):)
iter_shift:         3     5     7     9     11     13    *15     17     19     21      23
run time:           6s    6s    6s    6s    6s     6s     6s     7s     8s     11s     27s
legacy APIs: SP/SC: 47    20    13    22    54     83     91     73     81     75      95
legacy APIs: MP/MC: 44    18    18    240   245    270    250    249    252    250     253

aarch64-n1sdp:
$sudo ./app/test/dpdk-test -l 1-2
Testing using two physical cores(bulk (size: 8):)
iter_shift:         3     5     7     9     11     13    *15     17     19     21      23
run time:           8s    8s    8s    8s    8s     8s     8s     9s     9s     11s     23s
legacy APIs: SP/SC: 0.7   0.4   1.2   1.8   2.0    2.0    2.0    2.0    2.0    2.0     2.0
legacy APIs: MP/MC: 0.3   0.4   1.3   1.9   2.9    2.9    2.9    2.9    2.9    2.9     2.9

According to above test data, when "iter_shift" is set as "15", the test
run time is reduced to less than 1 minute and the test result can keep
stable in x86 and aarch64 servers.

Fixes: 1fa5d0099efc ("test/ring: add custom element size performance tests")
Cc: stable@dpdk.org
Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>