MySQL, Innodb, DBT2 Core Scalability Graphs
2008-07-14 at 03:50 pm Matthew YonkovitI was at a client site with Yves Trudeau ( another MySQL consultant ) and the client had purchased a brand new top of the line 16 core server. It is well documented in many places that scalability beyond 4-8 cores with innodb is less then optimal. We were asked for a ballpark on the performance of a 16 cores vs an 8 cores, and specifically if their were any options to reduce the number of cores the mysqld process could use. We decided to benchmark this using DBT2. To do the test we ended up setting the CPU affinity of the mysqld process. You can set this with the following command: taskset. Yves ended up trying the same DBT2 tests for 1-16 cores. I won’t write too much about the scalability here, as I said their are way better resources out their that can explain it better, but what I wanted to do is post the results of the tests. Here they are:
As I said talked about elsewhere, but I have not seen a core by core break down of these #’s which paints an interesting picture. In these tests 6,7,8 cores were able to handle very similar numbers, 9+ cores see some drop off.
*** Forgot to mention this was 5.0.62 ***
*** Another thing for me to recheck is setting the affinity of mysqld, this may explain the reason 1 core vs 4 cores show little difference ***
Am I reading this correctly, that increasing the number of cores from 1 to 8 only increased the tpm by about 1.7 times? I know mysql isn’t the best scaling database, but this is far worse than I expected or I’ve seen. Was the, by chance, there an I/O bottleneck or some other issue?
wouldn’t put too much stock in the 1 core vs the 4 core numbers. The scalability with the lower numbers could be due to setting the affinity of processors or contention issues. These tests were run with 100 warehouses, 64 connections. The innodb buffer pool was set to 45GB, while the dataset size was 21GB. I have a small 4 core server I can see how setting the affinity setting affects the results and will post a followup.
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