Messages in this thread | | | Date | Fri, 05 Sep 2008 12:19:14 -0400 | From | "Alan D. Brunelle" <> | Subject | Benchmarking results: DSS elapsed time values w/ rq_affinity=0/1 - Jens' for-2.6.28 tree |
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Some DSS results from a 32-way ia64 machine set up to try and analyze Oracle OLTP & DSS loads (128GB RAM, >200 disks). The data collected was the elapsed time for DSS runs w/ 128 MBRs and 128 Readers, running on a kernel generated from Jens Axboe's origin/for-2.6.28 tree. I alternated runs, setting rq_affinity to 0 and 1 for all disks at the beginning of each run.
There are a total of 68 data points for each alternative, and the overall results show a decided improvement for this type of load with rq_affinity set to 1:
rq=0: min=27.440000 avg=27.980500 max=28.500000 sdev=0.296827 rq=1: min=26.900000 avg=27.071500 max=27.480000 sdev=0.125169
Not only do we see about a 3.25% improvement in reduced average time, we also see that the run-to-run deviations are much smaller as well. For a pictorial representation, check out the graph @
http://free.linux.hp.com/~adb/jens/08-09-05/dss.png
The red and green areas illustrate the delta from the average for all the data points with that rq_affinity setting. (Red being rq_affinity=0, green being rq_affinity=1.)
I collected some vmstat & iostat data, and will be evaluating that as well, and perhaps looking into lockstat & profiling data (time permitting).
The system has been set up as part of a collaboration between HP & Red Hat's Linux performance teams, and we've been using it to analyze performance characteristics of Oracle loads on large-ish systems, as well as for evaluating potential code changes.
Alan D. Brunelle HP Linux Kernel Technology Team
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