review request (M): 7121140: Allocation paths require explicit memory synchronization operations for RMO systems

[Roland Westrelin]

> I wouldn't expect this to affect performance since it's not emitting an extra instructions but we are emitting some extra barriers which tangles of the memory graph a bit.  Could you do some quick performance to make sure nothing's changed?

Below are the results. 

Roland.

============================================================================
tt1
  Benchmark         Samples        Mean     Stdev
  specjbb2005            10   196409.50      0.01
    peak                 10   219067.61      0.02
    peak_warehouse       10        4.00      0.00
    last                 10   196409.49      0.01
    interval_average     10    11553.50      0.01
    first                10    35924.81      0.01
    overall_average      10   167704.10      0.01
    last_warehouse       10        8.00      0.00
============================================================================
tt2
  Benchmark         Samples        Mean     Stdev   %Diff    P   Significant
  specjbb2005            10   196016.36      0.01   -0.20 0.737            *
    peak                 10   216797.36      0.02   -1.04 0.262            *
    peak_warehouse       10        4.00      0.00   -0.00 0.000            *
    last                 10   196016.35      0.01   -0.20 0.737            *
    interval_average     10    11530.40      0.01   -0.20 0.737            *
    first                10    35558.66      0.00   -1.02 0.000          Yes
    overall_average      10   167822.07      0.01    0.07 0.852            *
    last_warehouse       10        8.00      0.00   -0.00 0.000            *
============================================================================

============================================================================
t1
  Benchmark         Samples        Mean     Stdev
  specjvm98              10      667.76      0.00
    javac                10      392.03      0.01
    db                   10      438.88      0.00
    jess                 10      700.73      0.00
    jack                 10      594.09      0.01
    compress             10      536.31      0.00
    mtrt                 10     1808.20      0.02
    mpegaudio            10      852.60      0.01
============================================================================
t2
  Benchmark         Samples        Mean     Stdev   %Diff    P   Significant
  specjvm98              10      666.48      0.00   -0.19 0.183            *
    javac                10      391.46      0.01   -0.15 0.827            *
    db                   10      439.52      0.00    0.15 0.501            *
    jess                 10      701.00      0.01    0.04 0.870            *
    jack                 10      589.77      0.00   -0.73 0.006          Yes
    compress             10      537.17      0.01    0.16 0.534            *
    mtrt                 10     1788.32      0.02   -1.10 0.229            *
    mpegaudio            10      855.14      0.01    0.30 0.468            *
============================================================================