Ubuntu 32-bit, 32-bit PAE, and 64-bit kernel Performance Comparison

At the reader's request, phoronix.com recently conducted a special performance test on the Linux kernel, comparing the performance of 32-bit, 32-bit physical address extension (PAE), and 64-bit. Linus Torvalds, the father of Linux systems, once said that there is a 25% performance difference between the system kernel that enables and disables config_highmem4g (which enables 32-bit systems to support 4 GB physical memory. Here we will verify it.

This test uses the Lenovo ThinkPad t61 notebook and Ubuntu 9.10 system. The hardware configuration includes core 2 Duo t9300 processor, 4 GB memory, Hitachi 100 GB hts7220 SATA hard drive, and NVIDIA Quadro NVS 140m graphics card, keep the default system and software configurations, including Linux 2.6.31 kernel, gnome 2.28.1 desktop environment, X Server 1.6.4, NVIDIA 195.22 graphics card driver, GCC 4.4.1 compiler, and ext4 file system.

Config_highmem4g is enabled for the 32-bit Ubuntu kernel by default, but the PAE mode is disabled. In this way, when the system configures 4 GB memory, 1 GB is reserved for the kernel virtual space. The actual available space is only 3 GB, the Ubuntu PAE kernel uses config_highmem64g, which can process a maximum of 64 GB memory. Of course, the 64-bit kernel does not have such memory addressing space limitations, which is also the trend of the future.

During the test, the Ubuntu 32-bit PAE mode has enabled swap, config_highmem64g instead of config_highmem4g, config_x86_pae, swap, swap, and disable config_async_tx_dma. The other 32-bit non-PAE mode is consistent.

After 14 tests, we found that Ubuntu uses a 32-bit common kernel or the 32-bit plus PAE mode kernel without any performance differences. After throwing away the error factors, the scores were all the same. Of course, the memory used here is only 4 GB, which is a common configuration for high-end users. You may see some performance differences after adding 8 GB, 16 GB or more.

At the same time, we can also see that the performance advantage of the 64-bit kernel is very obvious, go out of the first "openarena" (the open source content package of the thunder hammer 3 arena) game all in the leading, the game speed is even scary (17 times in Apache testing), so unless there are technical reasons or environmental restrictions, large Memory users do not need to struggle with the 32-bit kernel and the PAE mode, and going straight to the 64-bit kernel is king.