some performance problem when test 4 cores SMP benchmark of seL4bench project

2 Dec 2021

      Hi,
  Now, I meet some performance problem when test 4 cores SMP benchmark of seL4bench on our platform.
  Out platform is XXX, But I get the test data of IMX8MM_EVK_64 and TX2 platform from seL4 website, I think they are official statistics.
  My test results below:
                                                                        ARM platform
        Test item                         XXX                  IMX8MM_EVK_64          TX2
                                             mean(Stddev)
       500 cycles, 1 core        636545(46)            625605(29)            598142(365)
       500 cycles, 2 cores      897900(2327)      1154209(44)           994298(94)
       500 cycles, 3 cores     1301679(2036)      1726043(65)        1497740(127)
       500 cycles, 4 cores     1387678(549)       2172109(12674)   1545872(109)
      1000 cycles, 1 core       636529(42)            625599(22)            597627(161)
      1000 cycles, 2 cores      899212(3384)      1134110(34)          994437(541)
      1000 cycles, 3 cores     1297322(5028)      1695385(45)        1497547(714)
      1000 cycles, 4 cores     1387149(456)        2174605(81)        1545716(614)

   From these compare data:

  1.  When test smp bench on one core, the performance of several platform is similar
  2.  When test smp bench on muti core, the result of IMX8MM_EVK_64 is beauty, the result of 4 cores is 3.47 times as good as 1 core, I think it’s good
  3.  But the platform of TX2 has some different performance, the result of 2 cores is 1.66 times as good as 1 core, I still think is good, But the result of 3 cores almost have the same ping-pong count with 4 cores, why add one core, the count result not add as our expected ?
  4.  The performance of our platform is badly, on our platform, the result of 3 cores almost also have the same ping-pong count with 4 cores, and our count result of 4 cores just 2 times as good as one core, I think it is very bad
  5.  I want to know what are the possible causes of the badly performance about our platform XXX and TX2 ?

yadong.li

Gernot Heiser

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