HP-UX Reference (11i v2 04/09) - 5 Miscellaneous Topics (vol 9)

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vxfs_bc_bufhwm(5) vxfs_bc_bufhwm(5)

(Tunable Kernel Parameters)

NAME

vxfs_bc_bufhwm - VxFS buffer cache high water mark(determines the VxFS buffer cache size)

SYNOPSIS

/usr/bin/kctune -s vxfs_bc_bufhwm={maximum size of buffer cache}

VALUE

Specify an integer value.

Minimum

6144 KB

Maximum

None

Default

DESCRIPTION

VxFS maintains a buffer cache in the kernel for frequently accessed ﬁle system metadata in addition to

the HP-UX kernel buffer cache that caches the ﬁle data.

vxfs_bc_bufhwm

tunable parameter deter-

mines the size of the VxFS buffer cache (the maximum amount of memory that can be used to cache VxFS

metadata).

The default value computed based on the amount of system memory ensures good system performance

across a wide range of applications.

The value of

vxfs_bc_bufhwm

is speciﬁed in kilobytes. To improve performance during application

loads that cause frequent ﬁle system metadata changes on the system (for example, a high rate of ﬁle

creation or deletion, or accessing large directories), change the value of

vxfs_bc_bufhwm.

Notes

Use the

vxfsstat command to monitor buffer cache statistics and inode cache usage.

EXAMPLES

Set the maximum of size of buffer cache at 300000:

# kctune -s vxfs_bc_bufhwm=300000

WARNINGS

All HP-UX kernel tunable parameters are release speciﬁc. This parameter may be removed or its mean-

ing may change in the future releases of HP-UX.

Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parame-

ter values. After installation, some tunable parameters may no longer be at the default or recommended

values. For information about the effects of installation on tunable values, consult the documentation for

the kernel software being installed. For information about optional kernel software that was factory

installed on your system, see HP-UX Release Notes at

http://docs.hp.com.