dump cache performance

[Peter Jeremy]

On 2010-Oct-24 18:05:05 +0200, Jean-Francois Dockes <jf at dockes.org> wrote:
>It appears that modifying dump to use a shared cache in a very simple way
>(move the control structures to the shared segment and perform simple locking)
>yields substantial speed increases.

Indeed.  That's better than I expected.

>Would someone be interested in reviewing the patch and/or perform
>more tests ?

I've mostly convered to ZFS but still have UFS root (which is basically
a full base install without /var but including /usr/src - 94k inodes
and 1.7GB).  I've run both the 8-stable ("stable") and patched ("jfd") dump 
alternately 4 times with 50/250MB cache with the following results:

x stable
+ jfd
+------------------------------------------------------------+
|                                                           +|
|                                                           +|
|  x                                                        +|
|x xx                                                       +|
||AM                                                        A|
+------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   4          9413          9673          9568        9555.5     107.12143
+   4         15359         15359         15359         15359             0
Difference at 95.0% confidence
        5803.5 +/- 131.063
        60.7347% +/- 1.3716%
        (Student's t, pooled s = 75.7463)

-- 
Peter Jeremy
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