Chapter 2
Solaris Kernel Tunables
This section describes most of the Solaris kernel tunables.
Where to Find Tunable Parameter Information
General Parameters
This section describes general kernel parameters relating to physical
memory and stack size.
physmem
| Description | Modifies the system's
idea of the number of physical pages of memory after the OS and firmware are
accounted for.
|
| Data Type | Unsigned long
|
| Default | Number of usable pages of
physical memory available on the system--not counting the memory where
the core kernel and data are stored.
|
| Range | 1 to amount of physical memory
on system
|
| Units | Pages
|
| Dynamic? | No
|
| Validation | None
|
| When to Change | Whenever you want
to test the effect of running with less physical memory. Note that because
this parameter does not take into account the memory
used by the core kernel and data as well as various other data structures
allocated early in the startup process, the value of physmem
should be less than the actual number of pages that represent the smaller
amount of memory.
|
| Commitment Level | Unstable
|
lwp_default_stksize
| Description | Default value of size
of stack to be used when a kernel thread is created, and the calling routine
does not provide an explicit size to be used.
|
| Data Type | Integer
|
| Default | 8192 for all 32-bit SPARC
and IA based platforms
16,384 for 64-bit sun4u platforms
|
| Range | 0 to 262,144
|
| Units | Bytes in multiples of the
value returned by getpagesize(3C).
|
| Dynamic? | Yes. Affects threads created
after the variable is changed.
|
| Validation | Must be greater than
or equal to 8192 and less than or equal to 262,144 (256 x 1024) and must be
a multiple of the system page size. If these conditions are not met, the following
message is displayed:
Illegal stack size, Using N
|
The value of N is the default described above.
|
| When to Change | When the system panics
because it has run out of stack space. The best solution for this problem
is to determine why the system is running out of space and make a correction.
Increasing the default stack size means that almost every kernel thread will
have a larger stack, resulting in increased kernel memory consumption for
no good reason, because that space will generally be unused. The increased
consumption means that other resources competing for the same pool of memory
will have the amount of space available to them reduced, possibly decreasing
the system's ability to perform work. Among the side effects will be a reduction
in the number of threads which the kernel can create. This solution should
be treated as no more than an interim workaround until the root cause is remedied.
|
| Commitment Level | Unstable
|
