STREAMS parameters

Parameter	Dflt	Min	Max
LOGHIWAT	8192	8192	16384
LOGLOWAT	256	128	512
NAUTOPUSH	32	16	48
NLOG	10	3	16
NSTRPHASH	64	16	512
NSTRPUSH	9	9	10
NUMSAD	8	1	16
STRCTLSZ	1024	1024	2048
STRNSCHED	16	1	32
STRMSGSZ	65536	0	65536
STRTHRESH	0	0	0x1000000

LOGHIWAT

The high water mark (in bytes) for the log driver. High and low water marks are used by STREAMS for flow control. When debugging modules and drivers, strace(1M) can be used. If the messages are generated too quickly, strace may lose some of them. Setting these values allows you to control the amount of data that flows through the driver to prevent messages from being lost.

LOGLOWAT

The low water mark (in bytes) for the log driver. See LOGHIWAT for more information.

NAUTOPUSH

The number of devices that can be configured to be autopushed.

NLOG

The number of STREAMS loggers. The number of minor devices that are available through the clone interface of the log driver (/dev/log). If an open of /dev/log fails with errno set to ENXIO, this number might need to be increased.

NSTRPHASH

This is the size of an internal hash table used by the STREAMS autopush daemon. This will probably never need to be changed unless the number of drivers on the system gets very large. It must be a power of ``2''.

NSTRPUSH

The maximum number of modules that can be pushed onto a Stream. This is used to prevent an errant user process from consuming all the available queues on a single Stream. By default this value is ``9'', but in practice, existing applications have pushed, at most, four modules on a Stream.

NUMSAD

The number of minor devices that are available through the Streams Administration Driver (SAD).

STRCTLSZ

The maximum allowable size of the control portion of any STREAMS message. The control portion of a putmsg(2) message is not subject to the constraints of the minimum or maximum packet size, so entering a value here is the only way of providing a limit for the control part of a message. The recommended value of ``1024'' is more than enough for existing applications.

STRNSCHED

Maximum number of service procedures to run in any given runqueues invocation.

STRMSGSZ

The maximum allowable size of the data portion of any STREAMS message. This should be set large enough to accommodate the maximum packet size restrictions of all configured STREAMS modules. A value of zero indicates no upper bound.

STRTHRESH

The maximum number of bytes STREAMS can allocate. When the threshold is passed, users without appropriate privilege are not allowed to open streams, push streams modules, nor execute writes to streams devices. These operations will fail with ENOSR, out of streams resources. Note that the threshold applies to the output side only and data coming into the system (for example, console) is not affected and will continue to work properly. The default value is zero to indicate that there is no threshold. This value can be reset by the administrator with appropriate privilege if a naive or malicious user runs the machine out of memory. Then, the setting should be based on the memory size of the machine.