Thursday, July 06, 2006

HP-UX Memory Page Size Tuning With chatr

Useful links.

HP-UX Kernel Tuning and Performance Guide, from 2000. Mostly versions 9 and 10, with a section on 11.0.

chatr information.
chatr +pd=256M +pi=16M progname.x
This will increase the data page size to 256MB and the instruction page size to 16MB. This will result in fewer virtual memory pages, and hence requires fewer page translation entries in the tlb.

chatr information.
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:
+pd size -- requests a specified data page size of 4K bytes,
16K, 64K, 256K, 1M, 4M, 16M, 64M, 256M, or L. Use L to
specify the largest page size available. The actual page
size may vary if the requested size can not be fulfilled.
+pi size -- requests a specified instruction page size. (See
+pd size for size values.). 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.
To set the virtual memory page size by using the linker:
ld +pd 64K +pi 16K /opt/langtools/lib/crt0.o myprog.o -lc
To set the page size by using chatr:
chatr +pd 64K +pi 16K a.out
See also “Performance Optimized Page Sizing”:

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