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Oracle Solaris Tunable Parameters Reference Manual Oracle Solaris 11 Information Library |
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Oracle Solaris Tunable Parameters Reference Manual Oracle Solaris 11 Information Library |
1. Overview of Oracle Solaris System Tuning
2. Oracle Solaris Kernel Tunable Parameters
Where to Find Tunable Parameter Information
fsflush and Related Parameters
General File System Parameters
SPARC System Specific Parameters
4. Internet Protocol Suite Tunable Parameters
5. Network Cache and Accelerator Tunable Parameters
A. Tunable Parameters Change History
This section describes general kernel parameters that are related to physical memory and stack configuration.
Modifies the system's configuration of the number of physical pages of memory after the Oracle Solaris OS and firmware are accounted for.
Unsigned long
Number of usable pages of physical memory available on the system, not counting the memory where the core kernel and data are stored
1 to amount of physical memory on system
Pages
No
None
Whenever you want to test the effect of running the system with less physical memory. 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.
Unstable
Determines the minimum size of the ZFS Adaptive Replacement Cache (ARC). See also zfs_arc_max.
Unsigned Integer (64-bit)
64 MB
64 MB to zfs_arc_max
Bytes
No
Yes, the range is validated.
When a system's workload demand for memory fluctuates, the ZFS ARC caches data at a period of weak demand and then shrinks at a period of strong demand. However, ZFS does not shrink below the value of zfs_arc_min. Generally, you do not need to change the default value.
Unstable
For information, see zfs_arc_min (Oracle Solaris 11).
Determines the maximum size of the ZFS Adaptive Replacement Cache (ARC). See also zfs_arc_min.
Unsigned Integer (64-bit)
Three-fourths of memory on systems with less than 4 GB of memory
physmem minus 1 GB on systems with greater than 4 GB of memory
64 MB to physmem
Bytes
No
Yes, the range is validated.
If a future memory requirement is significantly large and well defined, you might consider reducing the value of this parameter to cap the ARC so that it does not compete with the memory requirement. For example, if you know that a future workload requires 20% of memory, it makes sense to cap the ARC such that it does not consume more than the remaining 80% of memory.
Unstable
For information, see zfs_arc_max (Oracle Solaris 11).
Specifies the default stack size of all threads. No thread can be created with a stack size smaller than default_stksize. If default_stksize is set, it overrides lwp_default_stksize. See also lwp_default_stksize.
Integer
3 x PAGESIZE on SPARC systems
5 x PAGESIZE on x64 systems
Minimum is the default values:
3 x PAGESIZE on SPARC systems
5 x PAGESIZE on x64 systems
Maximum is 32 times the default value.
Bytes in multiples of the value returned by the getpagesize parameter. For more information, see getpagesize(3C).
Yes. Affects threads created after the variable is changed.
Must be greater than or equal to 8192 and less than or equal to 262,144 (256 x 1024). Also 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 value of default_stksize.
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 then 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. Generally, that space will be unused. The increased consumption means other resources that are 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 is a reduction in the number of threads that the kernel can create. This solution should be treated as no more than an interim workaround until the root cause is remedied.
Unstable
Specifies the default value of the stack size to be used when a kernel thread is created, and when the calling routine does not provide an explicit size to be used.
Integer
24,576 for SPARC platforms
20,480 for x64 platforms
Minimum is the default values:
3 x PAGESIZE on SPARC systems
5 x PAGESIZE on x64 systems
Maximum is 32 times the default value.
Bytes in multiples of the value returned by the getpagesize parameter. For more information, see getpagesize(3C).
Yes. Affects threads created after the variable is changed.
Must be greater than or equal to 8192 and less than or equal to 262,144 (256 x 1024). Also 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 value of lwp_default_stksize.
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 then 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. Generally, that space will be unused. The increased consumption means other resources that are 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 is a reduction in the number of threads that the kernel can create. This solution should be treated as no more than an interim workaround until the root cause is remedied.
Unstable
Maximum number of system events allowed to be queued and waiting for delivery to the syseventd daemon. Once the size of the system event queue reaches this limit, no other system events are allowed on the queue.
Integer
5000
0 to MAXINT
System events
Yes
The system event framework checks this value every time a system event is generated by ddi_log_sysevent and sysevent_post_event.
For more information, see ddi_log_sysevent(9F) and sysevent_post_event(3SYSEVENT).
When error log messages indicate that a system event failed to be logged, generated, or posted.
Unstable
Specifies the amount of kernel pageable memory available. This memory is used primarily for kernel thread stacks. Increasing this number allows either larger stacks for the same number of threads or more threads. A system running a 64-bit kernel uses a default stack size of 24 KB.
Unsigned long
2 GB
512 MB to 24 GB
8-KB pages
No
Value is compared to minimum and maximum sizes (512 MB and 24 GB). If smaller than the minimum or larger than the maximum, it is reset to 2 GB. A message to that effect is displayed.
The actual size used in creation of the cache is the lesser of the value specified in segkpsize after the validation checking or 50 percent of physical memory.
Required to support large numbers of processes on a system. The default size of 2 GB, assuming at least 1 GB of physical memory is present. This default size allows creation of 24-KB stacks for more than 87,000 kernel threads. The size of a stack is the same, whether the process is a 32-bit process or a 64-bit process. If more than this number is needed, segkpsize can be increased, assuming sufficient physical memory exists.
Unstable
Enables the stack to be marked as nonexecutable, which helps make buffer-overflow attacks more difficult.
An Oracle Solaris system running a 64-bit kernel makes the stacks of all 64-bit applications nonexecutable by default. Setting this parameter is necessary to make 32-bit applications nonexecutable.
Signed integer
0 (disabled)
0 (disabled) or 1 (enabled)
Toggle (on/off)
Yes. Does not affect currently running processes, only processes created after the value is set.
None
Should be enabled at all times unless applications are deliberately placing executable code on the stack without using mprotect to make the stack executable. For more information, see mprotect(2).
Unstable
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