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Oracle Solaris 11.1 Tunable Parameters Reference Manual     Oracle Solaris 11.1 Information Library
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Document Information

Preface

1.  Overview of Oracle Solaris System Tuning

2.  Oracle Solaris Kernel Tunable Parameters

Where to Find Tunable Parameter Information

General Kernel and Memory Parameters

physmem

default_stksize

lwp_default_stksize

logevent_max_q_sz

segkpsize

noexec_user_stack

fsflush and Related Parameters

fsflush

tune_t_fsflushr

autoup

dopageflush

doiflush

Process-Sizing Parameters

maxusers

reserved_procs

pidmax

max_nprocs

maxuprc

ngroups_max

Paging-Related Parameters

lotsfree

desfree

minfree

throttlefree

pageout_reserve

pages_pp_maximum

tune_t_minarmem

fastscan

slowscan

min_percent_cpu

handspreadpages

pages_before_pager

maxpgio

Swapping-Related Parameters

swapfs_reserve

swapfs_minfree

Kernel Memory Allocator

kmem_flags

kmem_stackinfo

General Driver Parameters

moddebug

ddi_msix_alloc_limit

Network Driver Parameters

igb Parameters

mr_enable

intr_force

ixgbe Parameters

tx_queue_number

rx_queue_number

intr_throttling

rx_limit_per_intr

tx_ring_size

rx_ring_size

tx_copy_threshold

rx_copy_threshold

General I/O Parameters

maxphys

rlim_fd_max

rlim_fd_cur

General File System Parameters

ncsize

dnlc_dir_enable

dnlc_dir_min_size

dnlc_dir_max_size

dnlc_dircache_percent

TMPFS Parameters

tmpfs:tmpfs_maxkmem

tmpfs:tmpfs_minfree

Pseudo Terminals

pt_cnt

pt_pctofmem

pt_max_pty

STREAMS Parameters

nstrpush

strmsgsz

strctlsz

System V Message Queues

System V Semaphores

System V Shared Memory

segspt_minfree

Scheduling

disp_rechoose_interval

Timers

hires_tick

timer_max

SPARC System Specific Parameters

tsb_alloc_hiwater_factor

default_tsb_size

enable_tsb_rss_sizing

tsb_rss_factor

Locality Group Parameters

lpg_alloc_prefer

lgrp_mem_pset_aware

3.  Oracle Solaris ZFS Tunable Parameters

4.  NFS Tunable Parameters

5.  Internet Protocol Suite Tunable Parameters

6.  System Facility Parameters

A.  Tunable Parameters Change History

B.  Revision History for This Manual

Index

General I/O Parameters

maxphys

Description

Defines the maximum size of physical I/O requests. If a driver encounters a request larger than this size, the driver breaks the request into maxphys sized chunks. File systems can and do impose their own limit.

Data Type

Signed integer

Default

131,072 (sun4u or sun4v) or 57,344 (x86). The sd driver uses the value of 1,048,576 if the drive supports wide transfers. The ssd driver uses 1,048,576 by default.

Range

Machine-specific page size to MAXINT

Units

Bytes

Dynamic?

Yes, but many file systems load this value into a per-mount point data structure when the file system is mounted. A number of drivers load the value at the time a device is attached to a driver-specific data structure.

Validation

None

When to Change

When doing I/O to and from raw devices in large chunks. Note that a DBMS doing OLTP operations issues large numbers of small I/Os. Changing maxphys does not result in any performance improvement in that case.

Commitment Level

Unstable

rlim_fd_max

Description

Specifies the “hard” limit on file descriptors that a single process might have open. Overriding this limit requires superuser privilege.

Data Type

Signed integer

Default

65,536

Range

1 to MAXINT

Units

File descriptors

Dynamic?

No

Validation

None

When to Change

When the maximum number of open files for a process is not enough. Other limitations in system facilities can mean that a larger number of file descriptors is not as useful as it might be. For example:

  • A 32-bit program using standard I/O is limited to 256 file descriptors. A 64-bit program using standard I/O can use up to 2 billion descriptors. Specifically, standard I/O refers to the stdio(3C) functions in libc(3LIB).

  • select is by default limited to 1024 descriptors per fd_set. For more information, see select(3C). A 32-bit application code can be recompiled with a larger fd_set size (less than or equal to 65,536). A 64-bit application uses an fd_set size of 65,536, which cannot be changed.

An alternative to changing this on a system wide basis is to use the plimit(1) command. If a parent process has its limits changed by plimit, all children inherit the increased limit. This alternative is useful for daemons such as inetd.

Commitment Level

Unstable

rlim_fd_cur

Description

Defines the “soft” limit on file descriptors that a single process can have open. A process might adjust its file descriptor limit to any value up to the “hard” limit defined by rlim_fd_max by using the setrlimit() call or by issuing the limit command in whatever shell it is running. You do not require superuser privilege to adjust the limit to any value less than or equal to the hard limit.

Data Type

Signed integer

Default

256

Range

1 to MAXINT

Units

File descriptors

Dynamic?

No

Validation

Compared to rlim_fd_max. If rlim_fd_cur is greater than rlim_fd_max, rlim_fd_cur is reset to rlim_fd_max.

When to Change

When the default number of open files for a process is not enough. Increasing this value means only that it might not be necessary for a program to use setrlimit to increase the maximum number of file descriptors available to it.

Commitment Level

Unstable