Oracle optimization, NUMA architecture and Intel Nehalem CPU

Fenng went to the Oracle Open World conference the day before yesterday and shared his experiences on Oracle Optimization on his blog.

At Oracle Open World, Steve Shaw, the author of Hammerora, gave a speech about Oracle Optimization on the Linux platform, focusing on the NUMA architecture for Intel Nehalem CPUThe impact of running Oracle on performance.

For traditional SMP, increasing the CPU may not necessarily improve the system performance, because the shared system bus limits the CPUThe larger the number of CPUs, the larger the internal traffic, the more likely the shared bus is to reach the bottleneck. The NUMA architecture relieves the scalability problem by providing separate local memory for each core to improve scalability. The access time of each core to the local memory is different from that of other cores. Therefore, the application level is very important for memory access. From hardware to operating system to application, NUMA must be supported to make full use of real processing capabilities.

Here, We can insert Amdahl's Law to introduce Amdahl's Law. This Law points out that the speed in the parallel processor environment is subject to the serial part of the program, that is to say, it implies that multi-core performance may not be so good.

For a DBAIntel's Nehalem CPU(The structure is shown on the right) The most noteworthy feature is the improvement in the NUMA (Non-Uniform Memory Access) architecture.

The Oracle Database 8i supports the NUMA feature. NUMA is enabled by default on 10.2.0.4 and 11.1. However, this feature is disabled in earlier versions and later versions. On the Intel Platform, Oracle Validated RPMAfter the package is installed, NUMA is activated. During installation, when Oracle detects that the hardware and Operating System Support NUMA, it automatically enables NUMA support. Linux automatically supports NUMA after Kernel 2.6.9-67. If the hardware supports enable, enable is activated by default. To enable the function at the operating system level, add numa = off as the core parameter.

You can use the operating system command to view the related status:

# numactl --show

NUMA, a commonly seen term, does not seem to have obtained DBAWe pay enough attention to it. Note that the hardware, operating system, and application software (Oracle) must support NUMA to make full use of this feature. In theory, the use of memory requests should be more effective for DB environments that support NUMA. As for the specific performance data, we need to look at the actual test results. I am afraid it is difficult to give them for the time being. I will leave it for future Supplements. It must be said that, as a DBA, you must understand the ins and outs of a feature and its potential impact when enabling a feature.

Additional reading materials

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For software that cannot fully utilize multiple cores, such as some Web servers or proxies, consider how to utilize the NUMA feature.

Original article title: NUMA architecture and database performance

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