Param. kernel

vendredi 17 avril 2009
par  Jerome ROBERT
popularité : 5%

Configurable Kernel Parameters

Certain kernel operating parameters can be configured to fit specific
system needs, resulting in better performance or more effective
allocation of resources. The ideal value for each parameter is often
determined by the system’s particular hardware configuration, the
specific mix of applications the system runs, and the trustworthiness of
system users ; factors that vary widely from system to system.

HP attempts to provide reasonable default parameter settings, but you
may find it necessary or beneficial to modify these settings to better
suit the needs of your particular system’s users. Use the list below to
obtain detailed information about each configurable kernel parameter.

Note that individual parameters usually pertain to a specific subsystem ;
some are independent, but others are interrelated or interact with each
other. The following list of online help topics for each parameter is
grouped according to subsystem.

Warning

Changing kernel parameters to improper or inappropriate values or
combinations of values can cause data loss, system panics, or other
(possibly very obscure and/or difficult to diagnose) operating
anomalies, depending on which parameters are set to what values.

  • Before altering the value of any configurable kernel parameter,
    be sure you know the implications of making the change.
  • Never set any system parameter to a value outside the allowable
    range for that parameter (SAM refuses to store values outside of
    the allowable range).
  • Many parameters interact, and their values must be selected in a
    balanced way.

Discrepancies

As technological advances expand system size and capabilities, it is not
uncommon for maximum and/or default values of certain parameters to
change between releases or to vary between 32-bit and 64-bit processors.
The information provided in the documents associated with this web page
are believed to be accurate as of the time they were produced. However,
system changes may occasionally result in discrepancies between the
document and what is actually present on your system.

If you encounter any such discrepancies in any stated default or limit
values, consult the files in /etc/conf/master.d on your
system to determine the actual values for your machine.

Accounting Subsystem

Asynchronous I/O Subsystem

Dump Parameters

Fiber Channel Subsystem

Mass-Storage Subsystem

  • Overview of
    File System Kernel Parameters
  • List of
    File System Kernel Parameters
  • Configurable File System Buffer-Cache Parameters :
    bufpages
    Pages of static buffer cache
    dbc_min_pct
    Minimum dynamic buffer cache
    dbc_max_pct
    Maximum dynamic buffer cache
    nbuf
    Number of static buffer headers
  • Configurable Open or Locked Files Parameters :
    maxfiles
    soft limit for open files
    maxfiles_lim
    hard limit for open files
    nfile

    system-wide open-files limit

    nflocks
    system-wide file-lock limit
    ninode
    Maximum open inodes in memory
  • Configurable Asynchronous Write Parameter :
    fs_async
    Enable/disable asynchronous disk writes
  • Configurable VxFS (Journaled) File-System Parameter :
    vx_ncsize
    Memory space reserved for VxFS directory path-name cache

Logical Volume Manager (LVM)

Memory Swap Subsystem

Process Management Subsystem

Character-Mode I/O Streams Parameters

  • Overview of
    Character-Mode I/O Streams Parameters
    NSTRBLKSCHED
    Factory use only. Do not change value.
    NSTREVENT
    Maximum number of outstanding streams bufcalls that are allowed to exist at any given time on the system.
    NSTRPUSH
    Maximum number of streams modules that are allowed to exist in any single stream at any given time on the system.
    NSTRSCHED
    Maximum number of streams scheduler daemons that are allowed to run at any given time on the system.
    STRCTLSZ
    Maximum number of control bytes allowed in the control portion of any streams message on the system.
    STRMSGSZ
    Maximum number of bytes that can be placed in the data portion of any streams message on the system.
    nstrpty
    System-wide maximum number of streams-based PTYs that are allowed on the system.
    streampipes
    Force All Pipes to be Streams-Based

System V IPC Shared-Memory Subsystem

VME I/O Subsystem Parameters

Miscellaneous Parameters

Undocumented Parameters

Some parameters are not documented
for any of various reasons. Some are obsolete, some are associated
with independent software subsystems, some can result in severe system
malfunctions if they are altered without proper understanding, and some
are not supported by SAM.


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