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sys_attrs_generic(5)
NAME
sys_attrs_generic - system attributes for the generic kernel subsystem
DESCRIPTION
This reference page describes the attributes for the Generic (generic)
kernel subsystem.
Some of these attributes have corresponding parameters in the system
configuration file. If so, the corresponding parameter name in the system
configuration file is specified in parentheses following the attribute
name. In these cases, never edit the system configuration file to directly
change the value of the system parameter; change the attribute by using the
dxkerneltuner application, the /sbin/sysconfig -r command, or the
sysconfigdb command. See dxkerneltuner(8), sysconfig(8), and sysconfigdb(8)
for more information about your options for configuring kernel subsystems.
act_vers_high
A value that is set and used internally to support a rolling upgrade
operation in a TruCluster environment. Do not modify manually.
act_vers_low
A value that is set and used internally to support a rolling upgrade
operation in a TruCluster environment. Do not modify manually.
binlog_buffer_size
The kernel buffer size in bytes.
Default value: If the binlog_buffer_size is not explicitly specified,
the value for kernel buffer size is assigned at boot time and is based
on the amount of physical memory installed on the system. The value
assigned automatically ranges from 32 kilobytes to 1 megabyte.
Minimum value: 8192 (bytes, or 8 KB)
Maximum value: 1,048,576 (bytes, or 1 MB)
booted_args
The arguments that are passed from osf_boot to the kernel. This
attribute value is query only.
booted_kernel
The name of the kernel that was loaded by osf_boot. This attribute
value is query only.
clu_active_member
A value that indicates whether the system is (1) or is not (0) an
actively running member system in a TruCluster environment. This
query-only value is always set to 0 for a standalone system.
clu_configured
A value that indicates whether cluster kernel components are (1) or are
not (0) configured in the kernel. This query-only value is always set
to 0 for a standalone system.
compressed_dump
A value that enables (1) or disables (0) a compressed dump file. The
type of zero compression implemented for compression saves substantial
disk space but still allows the dump to be read by dbx and other
operating system tools.
Default value: 1 (enabled)
You might want to change the default value if you consistently use
tools, such as those from a third party, that do not support compressed
dump files. See the System Administration and the Kernel
Debuggingmanuals for more information about generating and working with
dump files.
cpu_enable_mask
A value for the bit mask that determines which CPUs are started in a
multi-CPU system. The lowest order bit (bit 0) in this mask
corresponds to CPU0. The next highest order bit corresponds to CPU1,
and so on, up to bit 63. The bits in these positions can be set to 0
(disabled) or 1 (enabled) for the corresponding CPU slots. The decimal
or hexidecimal value specified for cpu_enable_mask corresponds to the
binary value that has 0 and 1 in the correct ordinal positions for the
CPUs you want to enable or disable.
Default value: The hex value corresponding to the slots of CPUs that
are actually enabled. On single-CPU systems with the CPU in slot 0, the
default value is 0x1.
Minimum value: 0
Maximum value: 0xffffffffffffffff (or -1)
Specifying -1 for this attribute means that all CPUs present in the
system are allowed to be started by the master CPU. Specifying 0 for
this attribute enables uniprocessor operation in a multi-CPU system.
Other values enable and disable specific CPUs, depending on what the
system supports.
The following table illustrates the relationships between bit settings
and cpu_enable_mask values for enabling a single CPU. It is generally
easier to determine and enter hexidecimal values, so only a few
significant decimal equivalents are shown:
Bit Dec. Hex Single
63... 8 7 6 5 4 3 2 1 0 Value Value CPU Enabled
______________________________________________________________________
0 ... 0 0 0 0 0 0 0 0 0 0 0 Special meaning *
0 ... 0 0 0 0 0 0 0 0 1 1 0x1 CPU0
0 ... 0 0 0 0 0 0 0 1 0 0x2 CPU1
0 ... 0 0 0 0 0 0 1 0 0 0x4 CPU2
0 ... 0 0 0 0 0 1 0 0 0 0x8 CPU3
0 ... 0 0 0 0 1 0 0 0 0 0x10 CPU4
0 ... 0 0 0 1 0 0 0 0 0 0x20 CPU5
0 ... 0 0 1 0 0 0 0 0 0 0x40 CPU6
0 ... 0 1 0 0 0 0 0 0 0 0x80 CPU7
0 ... 1 0 0 0 0 0 0 0 0 0x100 CPU8
.
.
.
1 ... 0 0 0 0 0 0 0 0 0 0x8000000000000000 CPU63
* The minimum value (0) indicates that only the master (boot) CPU be
enabled. This value is useful if you want to test applications in a
uniprocessor environment and your test system normally runs in
multiprocessor mode.
Note
Some systems require that the master CPU be CPU0. For these systems,
0, 1, and 0x1 are equivalent entries and are the only values you
should specify for uniprocessor operation. On these systems, 0x1 is
always the value set for cpu_enable_mask because the kernel will
overwrite values specified for cpu_enable_mask that are incompatible
with having CPU0 as the master CPU. For other systems, users can
choose the slot position of the master CPU. Therefore, the result of
entering 0 for this attribute can vary. For example, the actual
setting would be 0x2 if CPU1 were the master CPU and 0x10 if CPU4
were the master CPU.
The following table illustrates the relationships between bit settings
and cpu_enable_mask values for enabling sample combinations of CPUs:
Bit Dec. Hex Multiple
63... 8 7 6 5 4 3 2 1 0 Value Value CPUs Enabled
_________________________________________________________________________
0 ... 0 0 0 0 0 0 0 1 1 0x3 CPU0, CPU1
0 ... 0 0 0 0 0 0 1 0 1 0x5 CPU0, CPU2
0 ... 0 0 0 0 0 0 1 1 0 0x6 CPU1, CPU2
0 ... 0 0 0 0 0 0 1 1 1 0x7 CPU0, CPU1, CPU2
.
0 ... 0 0 0 0 0 1 1 1 1 0xf CPU0 to CPU3
.
0 ... 0 0 0 0 1 1 1 1 1 0x1f CPU0 to CPU4
.
0 ... 0 0 0 1 1 1 1 1 1 0x3f CPU0 to CPU5
.
0 ... 0 0 1 1 1 1 1 1 1 0x7f CPU0 to CPU6
.
0 ... 0 1 1 1 1 1 1 1 1 0xff CPU0 to CPU7
.
0 ... 1 1 1 1 1 1 1 1 1 0x1ff CPU0 to CPU8
.
.
.
1 ... 1 1 1 1 1 1 1 1 1 -1 0xffffffffffffffff All available CPUs *
* The maximum value specifies 1 in all bit positions, thereby enabling
all available CPUs. This value corresponds to 18446744073709551615 or
-1 in decimal notation and 0xffffffffffffffff in hexidecimal notation.
You can enable and disable specific combinations of CPUs by entering
values that set and clear appropriate bit positions in the bit mask. If
you suspect that one of the CPUs on a multiprocessor system may be the
cause of a system problem, you can try running the system with
different combinations of available CPUs disabled to help confirm your
suspicion. Remember that if your system is one of those that require
CPU0 to be the master CPU, the kernel does not apply values that map to
0 in bit position 0. In this case, you have to switch another CPU into
slot 0 before you can do a test run that disables the CPU originally in
slot 0.
Certain lockmode attribute values override incompatible cpu_enable_mask
settings. If the value of the lockmode attribute is 0 or 1, all bits
in the cpu_enable_mask bit mask that do not correspond to the master
CPU are set to 0.
dump_allow_full_to_memory
For internal use only. Do not change this attribute value manually.
* dump_sp_threshold
A threshold size that determines whether single-partition or multiple-
partition dumps are created. If a dump will fit on the primary swap
partition and leave space that is equal to this threshold value, the
dump is created as a single-volume dump on the primary swap partition,
even if secondary swap partitions are available. (See the System
Administration and the Kernel Debugging manuals for details.)
Default value: 4096
Minimum value: 0
Maximum value: 4096
This value can be changed at run time.
dump_to_memory
A value that enables (1) or disables (0) dumping to memory.
Default value: 0 (disabled)
This value can be changed at run time; however, do so only under
direction of your support representative.
dump_user_pte_pages
A value that enables (1) or disables (0) the inclusion of user page
table entries in a crash dump. Normally, user page table entries
contribute no information about the cause of a system crash.
Default value: 0 (disabled)
This value can be changed at run time. However, you would normally
change it only when directed to do so by a support representative who
is gathering information about a particular problem.
* enable_async_printf
A value that enables (1) or disables (0) asynchronous printing of
messages to the console. Asynchronous printing to the console prevents
large numbers of messages from being written to the console at the same
time.
Default value: 1 (enabled)
This value can be changed at run time. Device driver developers need to
set enable_async_printf to 0 when debugging driver problems because
they need to see the results of kernel printf() calls at the time of
execution.
expect_1000b_to_compress_to
For internal use only. Do not set this attribute manually. See
expected_dump_compression.
* expected_dump_compression
The level of compression that a dump is typically expected to achieve.
Default value: 500
Minimum value: 0
Maximum value: 1000
This value can be changed at run time. See the System Administration
manual for instructions on how to calculate the typical dump
compression level for your system.
include_user_ptes_in_dumps
For internal use only. Do not set this attribute manually. See
dump_user_pte_pages.
* insecure_bind
A value that allows programmers to override file permissions when UNIX
domain sockets are created by a bind() call.
When insecure_bind is set to a value other than 0, UNIX domain sockets
are always created with mode 0777 (the umask is ignored). This
prevents bind: permission denied errors when the bind() call executes.
Default value: 0, meaning that file permission (umask) is not ignored
This value can be changed at run time. See bind(2) for more information
about creating domain sockets.
In a TruCluster environment, the value of this attribute must be the
same on all member systems.
kmem_audit_count
See kmem_debug.
kmem_debug
A value that enables (1) or disables (0) behavior useful for debugging
problems in kernel memory allocation.
Default value: 0
If enabled (1), each time the kernel memory allocator allocates or
deallocates memory in the kernel memory pool, the system checks whether
the operation is performed correctly. If the kernel memory pool is in a
corrupt state, the system crashes and provides useful debugging
information. This attribute, along with the kmem_audit_count,
kmem_debug_size_mask, kmem_protected_kmempercent, kmem_protected_lowat,
kmem_protected_size, and a series of kmemhighwater_* attributes should
be set only by or under the direction of kernel software developers or
support personnel.
kmem_debug_size_mask
See kmem_debug.
kmem_percent
The maximum percentage of kernel virtual address space that is reserved
for kernel memory allocator (malloc) memory.
Default value: Automatically set internally, depending on system memory
size.
Minimum value: 0
Maximum value: 100
If this value is too low, no space in map errors may occur and cause
the system to hang. However, this situation indicates an unexpected
problem that should be reported to your support representative. Do not
modify the default value for kmem_percent unless directed to do so by
your support representative.
kmem_protected_hiwat
See kmem_debug.
kmem_protected_kmempercent
See kmem_debug.
kmem_protected_lowat
See kmem_debug.
kmem_protected_size
See kmem_debug.
kmemhighwater_*
See kmem_debug.
* kmemreserve_percent
The percentage of memory that is reserved for the malloc component and
used for kernel memory allocations that are less than or equal to the
page size (8 KB).
Default value: 0, which actually specifies 0.4 percent of available
memory or 256 KB, whichever is smaller.
Minimum value: 1
Maximum value: 75
A heavy network load that results in dropped packets is the primary
reason why you might want to increase the kmemreserve_percent value.
The netstat -d -i or the vmstat -M command shows you whether there are
dropped packets. Increase the kmemreserve_percent value in small
increments until there are no entries in the fail_nowait column of the
vmstat -M command's output display.
This value can be modified at run time. However, once the value has
been increased, you cannot decrease it below 1 percent at run time. To
restore the default setting (which is calculated by the kernel), you
must directly edit the /etc/sysconfigtab file to remove or comment out
the attribute and then reboot the system. This restriction will be
removed in a future release. (Under ordinary conditions, direct editing
of the /etc/sysconfigtab file is a practice that is strongly
discouraged.)
leave_dumps_in_memory
For internal use only. Do not modify this attribute. See
dump_to_memory.
lite_system
A setting that enables (1) or disables (0) a set of attribute values
that improve performance for 32-MB systems. This attribute will soon
be obsolete. Most kernel components now determine memory size directly
and apply more sophisticated algorithms to determine defaults best
suited for the system.
Default value: 1 if memory size is less than or equal to 32 MB and 0 if
memory size is greater than 32 MB
Do not modify the default setting for this attribute unless instructed
to do so by support personnel or by patch kit documentation.
* live_dump_dir_name
The full path to the directory where live dumps are written. This
attribute allows you to write dumps generated while the system is
running to a directory other than the one where crash dumps are
written.
Default value: /var/adm/crash (same directory as used for crash dumps)
Minimum string length: 1 (byte)
Maximum string length: 65 (bytes)
This value can be modified at run time.
* live_dump_zero_suppress
A value that enables (1) or disables (0) zero compression of dumps that
are generated while the system is still running. The zero compression
process produces files that take longer to create but occupy less space
on disk.
Default value: 1 (enabled)
This value can be modified at run time. You might want to set this
value to 1 if you consistently use tools, such as those from third
parties, that do not support compressed dump files or you want dumps
created in a minimum amount of time. Because the system is still
running while a live dump is being created, some of the data in a live
dump may be inconsistent. The shorter creation time may result in less
data inconsistency.
See the Kernel Debugging and the System Administration manuals for more
information about creating and working with dump files.
lockdebug
A value that enables (1) or disables (0) lock debugging. If enabled
(1), the default value for the lockmode attribute is set to 4.
If you explicitly specify a value for the lockmode attribute, that
value also causes lockdebug to be set or reset (overridden). For
example, if you set lockmodeto be 0, 1, 2, or 3, the value of lockdebug
will be 0. If you set lockmode to be 4, the value of lockdebug will be
1.
Default value: 0 (disabled)
* lockmaxcycles
Used for internal debugging.
Default value: 0
Do not modify the default setting for this attribute unless instructed
to do so by support personnel or by patch kit documentation.
lockmode
The mode in which the simple lock primitive package is used within the
kernel. Mode settings support different combinations of real-time (RT)
kernel preemption, symmetric multiprocessing (SMP), and lock debugging
with lock statistics:
0 Neither RT nor SMP is required. In this case, the calls to the
simple lock primitives are patched out completely.
1 Only RT is required. In this case, the simple lock operations
maintain a "preemption blocking" count.
2 Only SMP is required. In this case, the lock operations provide
synchronization among multiple CPUs.
3 Both RT and SMP are required. In this case, lock operations
are performed as described for both mode 1 and 2.
4 Both RT and SMP are required. In this case, lock operations
are as described for mode 3, with the addition of kernel lock
debugging and statistics.
Default value: Assigned at boot time, depending on the values for the
rt_preempt_opt, cpu_enable_mask, and lockdebug attributes, and on
whether multiple CPUs are able to be booted.
If you specify a value for lockmode (0-4), your setting both overrides
the default setting and disables any of the three related capabilities
that cannot be supported by the chosen set of simple lock primitives.
For example, setting lockmode to 0, 1, 2, or 3 disables kernel lock
debugging and statistics, whether or not the lockdebug attribute was
originally set to 1 (to enable kernel lock debugging and statistics).
locktimeout
The number of seconds that a CPU will wait (spin) on a simple lock. If
a CPU cannot acquire a simple lock in the specified amount of time, a
fatal error occurs, and the system panics and issues a
"simple_lock:time limit exceeded" message.
Default value: 15 (seconds)
Do not modify the default setting for this attribute unless instructed
to do so by support personnel or by patch kit instructions. A 0 value
might cause boot failures on a multiprocessor system. Values larger
than the default might hang the system instead of causing it to panic
and reboot.
login_name_max
The maximum number of bytes supported for a user's login name string.
One byte may be equivalent to one character in many languages; however,
byte-to-character equivalence varies, depending on the user's default
locale.
Default value: 12 (bytes)
Minimum value: 9
Maximum value: 64
In a TruCluster environment, the value of this attribute must be the
same on all member systems.
The default 12-byte limit exists only for backward compatibility
reasons. Increase login_name_max to 64 to enable longer login names.
make_compressed_dumps
For internal use only. Do not modify this attribute. See
compressed_dump.
make_partial_dumps
For internal use only. Do not modify this attribute. See partial_dump.
max_lock_per_thread
The depth to which complex locks can be nested for a thread at one
time. The value of max_lock_per_thread is used for debugging (when
lockmode=4).
Default value: 16
Do not modify the default setting for this attribute unless instructed
to do so by support personnel or by patch kit documentation.
memberid
Cluster member ID in the range of 0 to 63 that is set only by
TruCluster software.
Default value: 0 (for standalone systems)
Minimum value: 0
Maximum value: 63
memberseq
Reserved for future use by TruCluster software.
memlimit
A kernel debugging value intended for internal use only.
memstr_buf_size
A kernel debugging value intended for internal use only.
memstr_end_addr
A kernel debugging value intended for internal use only.
memstr_start_addr
A kernel debugging value intended for internal use only.
msgbuf_size
The size (in bytes) of the message buffer that is used to store boot
log messages.
Default value: Set automatically, based on memory size.
Minimum value: 0 (bytes)
Maximum value: 1,048,576
You may need to increase this value on a large system that issues too
many boot messages for the buffer to hold until the syslog daemon
starts. If the buffer is too small, initial boot messages are not
written to the system log and the beginning of the first message that
is written is likely to be truncated.
new_vers_high
A value that is set and used internally to support a rolling upgrade
operation in a TruCluster environment. Do not modify manually.
new_vers_low
A value that is set and used internally to support a rolling upgrade
operation in a TruCluster environment. Do not modify manually.
old_obreak
A value that changes the behavior of an internal system call.
Default value: 1 (on)
Do not modify the default setting for this attribute unless instructed
to do so by support personnel or by patch kit documentation. Setting
this value to off (0) has a negative impact on system performance.
old_vers_high
A value that is set and used internally to support a rolling upgrade
operation in a TruCluster environment. Do not modify manually.
old_vers_low
A value that is set and used internally to support a rolling upgrade
operation in a TruCluster environment. Do not modify manually.
* partial_dump
A value that determines whether the system generates partial (1) or
full (0) crash dumps.
Default value: 1 (partial dumps are created)
You can modify this attribute at run time. See the Kernel Debugging and
the System Administration manuals for more information about creating
and working with dump files.
* physio_max_coalescing
A value that controls how I/O requests are gathered when readv or
writev operations are directed at a character device (not a block
device). For example, when set to 65536, eight 8-KB buffers coalesce
into one 64-KB buffer. This improves the efficiency of database
operations.
Default value: 65,536
Do not modify the default setting for this attribute unless instructed
to do so by support personnel or by patch kit documentation.
rolls_ver_lookup
A value that is set and used internally to support a rolling upgrade
operation in a TruCluster environment. Do not modify manually.
rt_preempt_opt
A value that enables (1) or disables (0) real-time kernel preemption.
Default value: 0 (disabled)
If real-time kernel preemption is enabled (1):
·
The default value for lockmode will be 1 on a single-CPU system or 3
on a multi-CPU system. However, if you explicitly specify certain
lockmode values, you implicitly override the rt_preempt_opt value.
For example, if you set lockmode to 0 or 2, you implicitly set
rt_preempt_opt to 0, disabling real-time kernel preemption.
·
The default value for ufs_lockholdmax will be 50. See
sys_attrs_ufs(5) for information on ufs_lockholdmax.
* use_faulty_fpe_traps
A value that restores (1) or corrects (0) backward-compatible but
incorrect behavior by the kernel's IEEE handler with respect to fast
mode floating-point exception traps.
When use_faulty_fpe_traps is set to 0, the IEEE handler correctly
returns a *_TRAP code for imprecise or invalid traps that cannot be
resolved and re-executed.
When use_faulty_fpe_traps is set to 1, the IEEE handler reverts to
returning a *_FAULT code for faulty traps that cannot be fixed and re-
executed. However, *_FAULT codes should be returned only when the
trap's trigger PC and instructions can still be determined; otherwise,
re-execution cannot be completed.
See ieee(3) and the Alpha Architecture Reference Manual for more
information on this topic.
Default value: 0 (correct return of *_TRAP code for faulty traps that
cannot be resolved and re-executed)
It is strongly recommended that you do not modify the default value.
* user_cfg_pt
The CFG run-time points that are configurable from user mode. Setting
this attribute to a particular value triggers kernel callbacks that
have been registered for the point corresponding to that value.
Default value: 45,000
Do not modify the default setting for this attribute unless instructed
to do so by support personnel or by patch kit documentation.
versw_switch
A value that is set and used internally to support a rolling upgrade
operation in a TruCluster environment. Do not modify manually.
versw_transition
A value that is set and used internally to support a rolling upgrade
operation in a TruCluster environment. Do not modify manually.
SEE ALSO
Commands: dxkerneltuner(8), sysconfig(8), sysconfigdb(8)
Others: sys_attrs(5)
System Configuration and Tuning
System Administration
Kernel Debugging
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