Re: [patch] Give kjournald a IOPRIO_CLASS_RT io priority

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Here are the results for the latest tests, some notes:

o The machine actually has 8GiB of RAM, so the tests still may end up using (some) page cache. (But at least it was the same for both kernels! :-) )

o Sorry the results took so long - the updated tree size caused the runs to take > 12 hours...

o The longer runs seemed to bring down the standard deviation a bit, although they are still quite large.

o 10 runs per test (read large file, read a tree, overwrite large file), with averages presented.

o 1st 4 columns (min, avg, max, std dev) refer to the average run lengths for the tests - real time, in seconds

o The last 3 columns are extracted from iostat results over the course of the whole run.

o The read a tree test certainly stands out - the other 2 large file manipulations have the two kernels within a couple of percent, but the read a tree test has Arjan's patch taking about 47%(!) longer on average. The increased %iowait & %system time in all 3 cases is interesting.


Read large file:

Kernel  Min    Avg    Max   Std Dev    %user  %system  %iowait
--------------------------------------------------------------
base :  201.6  215.1  275.5   22.8     0.26%    4.69%   33.54%
arjan:  198.0  210.3  261.5   18.5     0.33%   10.24%   54.00%

Read a tree:

Kernel  Min    Avg    Max   Std Dev    %user  %system  %iowait
--------------------------------------------------------------
base : 3518.2 4631.3 5991.3  784.6     0.19%    3.29%   23.56%
arjan: 5731.6 6849.8 7777.4  731.6     0.32%    9.90%   52.70%

Overwrite large file:

Kernel  Min    Avg    Max   Std Dev    %user  %system  %iowait
--------------------------------------------------------------
base :  104.2  147.7  239.5   38.4      0.02%    0.05%   1.08%
arjan:  106.2  149.7  239.2   38.4      0.25%    0.79%  14.97%

Let me know if there is anything else I can do to elaborate, or if you have suggestions for further testing.

Alan
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