I’ve been running a benchmark today on my old test box with conventional hard drives (no raid with BBU) and noticed something unusual in the CPU utilization statistics being reported.
The benchmark was run like this:
sysbench --num-threads=64 --max-requests=0 --max-time=600000 --report-interval=10 --test=oltp --db-driver=mysql --oltp-dist-type=special --oltp-table-size=1000000 --mysql-user=root --mysql-password=password run
Which means: create 64 threads and hammer the database with queries as quickly as possible. As the test was run on the localhost I would expect the benchmark to completely saturate the system – being either using CPU or being blocked on IO nature of this benchmark so it does not spend a lot on database locks, especially as this system has just 2 cores.
Looking at VMSTAT however I noticed this:
[root@smt1 mysql]# vmstat 10 procs -----------memory---------- ---swap-- -----io---- …[Read more]