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Controlling Memory Utilization of VxFS 3.5 on HP-UX 11i v2
Controlling the Buffer Cache
Appendix C158
Controlling the Buffer Cache
VxFS 3.5 implements a private buffer cache used exclusively for
metadata. The allocations made for this buffer cache are not static but
grow and shrink during system usage, depending on the load on the file
system. The global (static) tunable vx_bc_bufhwm represents the
maximum possible size of the VxFS buffer cache.
The maximum size of the metadata buffer cache is decided (auto-tuned)
at boot time based on system memory size, provided that the value of
vx_bc_bufhwm is set to zero (default).
As with the tunable vx_ninode, a large metadata buffer cache can help
improve file system performance especially during metadata-intensive
loads (stat, create, remove, link, lookup operations).
However, systems low on RAM (having typically 1GB/CPU or less) may
not need a large metadata buffer cache if the file system load is not
metadata-intensive or performance is not critical. In such circumstances,
the value of vx_bc_bufhwm can be manually tuned down, subject to a
minimum of 6144 (6MB).