Options to Improve TLB Hit Rates

To improve Translation Lookaside Buffer (TLB) hit rates in an application running on a PA 8000-based system, use the following linker or chatr virtual memory page setting options:

The default data and instruction page size is 4K bytes on PA-RISC systems.

The PA-RISC 2.0 architecture supports multiple page sizes, from 4K bytes to 64M bytes, in multiples of four. This enables large contiguous regions to be mapped into a single TLB entry. For example, if a contiguous 4MB of memory is actively used, 1000 TLB entries are created if the page size is 4K bytes, but only 64 TLB entries are created if the page size is 64K bytes.

Applications and benchmarks have larger and larger working-set sizes. Therefore, the linker and chatr TLB page setting options can help boost performance by improving TLB hit rates.

Some scientific applications benefit from large data pages. Alternatively, some commercial applications benefit from large instruction page sizes.