Re: Interleave factor performance impact

eaviles94_at_yahoo.com wrote:
> My test Oracle database server is performing better than my production
> database server.
>
> I've spent much time looking at database stats and tweaking different
> things at the database level but nothing has helped.
>
> One thing I noticed between the two servers is that the test box has
> all memory 16-way interleaved while the production box has a mix of
> 8-way and 16-way. I looked at memory configuration after I found memory
> intensive queries ran faster on test.
>
> How much impact does the interleave factor has on performance?

Others have suggested the best approach for tuning Oracle. Since I have never used Oracle, I can't comment on that.

This may be (probably is) too simplistic, but there is a program for testing memory bandwidth:

http://icl.cs.utk.edu/projects/llcbench/

This is the part of output I get from my Ultra 80. As you can see, figures in Mb/s drop quite dramatically at 4 MB, which I assume is because the cache size of the X1195A 450 MHz CPUs (there are 4) is 4 MB.

sparrow /export/home/drkirkby/llcbench/cachebench % ./cachebench

                 Memory Set Library Cache Test

C Size          Nanosec         MB/sec          % Chnge
-------         -------         -------         -------
256             0.75            1279.72         1.00
256             0.72            1316.86         0.97
384             0.61            1567.58         0.84
384             0.60            1585.15         0.99
512             0.54            1764.63         0.90
512             0.54            1752.30         1.01
768             0.48            2001.51         0.88
768             0.48            1990.85         1.01
1024            0.45            2136.23         0.93
1024            0.45            2121.47         1.01
1536            0.41            2304.18         0.92
1536            0.41            2307.56         1.00
2048            0.40            2391.77         0.96
2048            0.40            2393.02         1.00
3072            0.38            2482.46         0.96
3072            0.38            2493.88         1.00
4096            2.53            377.16          6.61
4096            2.58            370.25          1.02
6144            2.57            371.07          1.00

Of course you have a very different ssort of machine. Here's data from a similar is machine to the above. This time a Sun Ultra 60 with a single 360 MHz CPU. Again the cache size is 4 MB on this.

main-webserver # ./cachebench

                 Memory Set Library Cache Test

C Size          Nanosec         MB/sec          % Chnge
-------         -------         -------         -------
256             0.91            1052.24         1.00
256             0.91            1045.29         1.01
384             0.76            1248.05         0.84
384             0.76            1261.58         0.99
512             0.68            1404.07         0.90
512             0.68            1403.34         1.00
768             0.60            1590.35         0.88
768             0.61            1564.57         1.02
1024            0.56            1693.51         0.92
1024            0.56            1701.08         1.00
1536            0.52            1827.60         0.93
1536            0.53            1813.95         1.01
2048            0.50            1901.40         0.95
2048            0.50            1902.84         1.00
3072            0.48            1972.52         0.96
3072            0.48            1977.79         1.00
4096            1.43            666.12          2.97
4096            2.43            392.98          1.70
6144            2.41            396.41          0.99
6144            2.48            384.96          1.03

Anyway, it might confuse matters more, but the option is there of running that if you want. It was pretty easy to build.

-- 
Dave K

http://www.southminster-branch-line.org.uk/

Please note my email address changes periodically to avoid spam.
It is always of the form: month-year_at_domain. Hitting reply will work
for a couple of months only. Later set it manually. The month is
always written in 3 letters (e.g. Jan, not January etc)