Benchmarking mpsafevfs with parallel tarball extraction (ULE vs 4BSD)

[Kris Kennaway]

On Fri, May 06, 2005 at 11:35:29AM -0700, Kris Kennaway wrote:
> Here are my benchmark numbers for parallel tarball extraction
> with/without mpsafevfs on a 12-processor E4500 running up-to-date 6.0.
> Kernel was built without INVARIANTS and other debugging options,
> without ADAPTIVE_GIANT (which causes about a 200% performance penalty
> on system time in my testing, and has marginal impact on real or user
> time) and with 4BSD scheduler (ULE causes spontaneous reboots on this
> machine).  The e4500 uses the esp SCSI controller, which runs
> without Giant.

I tried with ULE on a quad amd64 machine, which was stable enough to
perform the extraction tests.  Here is the data for one tarball
extraction to md:

x real.one.4bsd
+ real.one.ule
+--------------------------------------------------------------------------+
|  +                                                                       |
|  +                                                                       |
|  +                                                                       |
|+ + + +                                                          x        |
|+ + + +                                                   x x  x x x x x x|
| |MA_|                                                       |___MA___|   |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   9          2.43           2.5          2.46     2.4644444   0.022973415
+  11          2.15          2.18          2.16     2.1636364   0.010269106
Difference at 95.0% confidence
        -0.300808 +/- 0.0161686
        -12.2059% +/- 0.656073%
        (Student's t, pooled s = 0.0171217)
...so ULE is 12% faster at extracting a single tarball to md

12 concurrent extractions:

x real.4bsd
+ real.ule
+--------------------------------------------------------------------------+
|        x    x                                          +   +             |
|x x   x x xx x   x                            +   + +   ++  + +      +   +|
|    |____AM___|                                   |______MA_______|       |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x  10         13.56         14.43         14.09         14.02     0.2641969
+  11         15.95         17.34         16.49     16.570909    0.40957184
Difference at 95.0% confidence
        2.55091 +/- 0.318571
        18.1948% +/- 2.27226%
        (Student's t, pooled s = 0.348356)

...but 18% slower with 12 concurrent extractions.  The effective
concurrency under 4BSD is 2.11 (same asymptote as on the 12-processor
sparc64, suggesting something universal like VFS locking is the
limitation) but under ULE it is only 1.57.

With 4 concurrent extractions (= # CPUs)

x real.4.4bsd
+ real.4.ule
+--------------------------------------------------------------------------+
|                           x                               +              |
|x                        xxx   x   x   x     * x  +     +  +  ++  + +    +|
|                 |____________AM____________|       |_______A_M_____|     |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x  10          4.65          5.44          5.17         5.157    0.22400645
+  10          5.41          5.87          5.69         5.657     0.1374409
Difference at 95.0% confidence
        0.5 +/- 0.174609
        9.69556% +/- 3.38587%
        (Student's t, pooled s = 0.185834)

ULE is still slower.  This suggests that at the present time (and
apart from the known instabilities) ULE may be better for filesystem
performance on lightly loaded systems, but it degrades worse than 4BSD
under concurrent filesystem load.

Kris

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