Performance tuning: HugePages in Linux
Recently we quickly and efficiently resolved a major performance issue with one of our New York clients. In this blog, I will discuss about this performance issue and its solution.
Problem statement
The client’s central database was intermittently freezing because of high CPU usage, and their business severely affected. They had already worked with vendor support and the problem was still unresolved.
Symptoms
Intermittent High Kernel mode CPU usage was the symptom. The server hardware was 4 dual-core CPUs, hyperthreading enabled, with 20GB of RAM, running a Red Hat Linux OS with a 2.6 kernel.
During this database freeze, all CPUs were using kernel mode and the database was almost unusable. Even log-ins and simple SQL such as SELECT * from DUAL; took a few seconds to complete. A review of the AWR report did not help much, as expected, since the problem was outside the database.
Analyzing the situation, collecting system activity reporter (sar) data, we could see that at 08:32 and then at 8:40, CPU usage in kernel mode was almost at 70%. It is also interesting to note that, SADC (sar data collection) also suffered from this CPU spike, since SAR collection at 8:30 completed two minutes later at 8:32, as shown below.
A similar issue repeated at 10:50AM: Read the rest of this entry . . .
