Newer
Older
may poison objects when not in use. Also tracks the
last alloc / free. For more information see
Documentation/vm/slub.txt.
Determines the maximum allowed order for slabs.
A high setting may cause OOMs due to memory
fragmentation. For more information see
Documentation/vm/slub.txt.
The minimum number of objects per slab. SLUB will
increase the slab order up to slub_max_order to
generate a sufficiently large slab able to contain
the number of objects indicated. The higher the number
of objects the smaller the overhead of tracking slabs
and the less frequently locks need to be acquired.
For more information see Documentation/vm/slub.txt.
slub_min_order= [MM, SLUB]
Determines the minimum page order for slabs. Must be
For more information see Documentation/vm/slub.txt.
slub_nomerge [MM, SLUB]
Disable merging of slabs with similar size. May be
necessary if there is some reason to distinguish
allocs to different slabs. Debug options disable
merging on their own.
For more information see Documentation/vm/slub.txt.
smart2= [HW]
Format: <io1>[,<io2>[,...,<io8>]]
smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
smsc-ircc2.ircc_sir= [HW] SIR base I/O port
smsc-ircc2.ircc_fir= [HW] FIR base I/O port
smsc-ircc2.ircc_irq= [HW] IRQ line
smsc-ircc2.ircc_dma= [HW] DMA channel
smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
0: Toshiba Satellite 1800 (GP data pin select)
1: Fast pin select (default)
2: ATC IRMode
softlockup_panic=
[KNL] Should the soft-lockup detector generate panics.
sonypi.*= [HW] Sony Programmable I/O Control Device driver
specialix= [HW,SERIAL] Specialix multi-serial port adapter
See Documentation/serial/specialix.txt.
spia_io_base= [HW,MTD]
spia_fio_base=
spia_pedr=
spia_peddr=
stacktrace [FTRACE]
Enabled the stack tracer on boot up.
stacktrace_filter=[function-list]
[FTRACE] Limit the functions that the stack tracer
will trace at boot up. function-list is a comma separated
list of functions. This list can be changed at run
time by the stack_trace_filter file in the debugfs
tracing directory. Note, this enables stack tracing
and the stacktrace above is not needed.
sti= [PARISC,HW]
Format: <num>
Set the STI (builtin display/keyboard on the HP-PARISC
machines) console (graphic card) which should be used
as the initial boot-console.
See also comment in drivers/video/console/sticore.c.
sti_font= [HW]
See comment in drivers/video/console/sticore.c.
stifb= [HW]
Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
sunrpc.min_resvport=
sunrpc.max_resvport=
[NFS,SUNRPC]
SunRPC servers often require that client requests
originate from a privileged port (i.e. a port in the
range 0 < portnr < 1024).
An administrator who wishes to reserve some of these
ports for other uses may adjust the range that the
kernel's sunrpc client considers to be privileged
using these two parameters to set the minimum and
maximum port values.
sunrpc.pool_mode=
[NFS]
Control how the NFS server code allocates CPUs to
service thread pools. Depending on how many NICs
you have and where their interrupts are bound, this
option will affect which CPUs will do NFS serving.
Note: this parameter cannot be changed while the
NFS server is running.
auto the server chooses an appropriate mode
automatically using heuristics
global a single global pool contains all CPUs
percpu one pool for each CPU
pernode one pool for each NUMA node (equivalent
to global on non-NUMA machines)
sunrpc.tcp_slot_table_entries=
sunrpc.udp_slot_table_entries=
[NFS,SUNRPC]
Sets the upper limit on the number of simultaneous
RPC calls that can be sent from the client to a
server. Increasing these values may allow you to
improve throughput, but will also increase the
amount of memory reserved for use by the client.
[KNL] Enable accounting of swap in memory resource
controller if no parameter or 1 is given or disable
it if 0 is given (See Documentation/cgroups/memory.txt)
swiotlb= [ARM,IA-64,PPC,MIPS,X86]
Format: { <int> | force }
<int> -- Number of I/O TLB slabs
force -- force using of bounce buffers even if they
wouldn't be automatically used by the kernel
sysfs.deprecated=0|1 [KNL]
Enable/disable old style sysfs layout for old udev
on older distributions. When this option is enabled
very new udev will not work anymore. When this option
is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
in older udev will not work anymore.
Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
the kernel configuration.
sysrq_always_enabled
[KNL]
Ignore sysrq setting - this boot parameter will
neutralize any effect of /proc/sys/kernel/sysrq.
Useful for debugging.
test_suspend= [SUSPEND]
Specify "mem" (for Suspend-to-RAM) or "standby" (for
standby suspend) as the system sleep state to briefly
enter during system startup. The system is woken from
this state using a wakeup-capable RTC alarm.
thash_entries= [KNL,NET]
Set number of hash buckets for TCP connection
thermal.act= [HW,ACPI]
-1: disable all active trip points in all thermal zones
<degrees C>: override all lowest active trip points
thermal.crt= [HW,ACPI]
-1: disable all critical trip points in all thermal zones
<degrees C>: override all critical trip points
thermal.nocrt= [HW,ACPI]
Set to disable actions on ACPI thermal zone
critical and hot trip points.
thermal.off= [HW,ACPI]
1: disable ACPI thermal control
thermal.psv= [HW,ACPI]
-1: disable all passive trip points
<degrees C>: override all passive trip points to this
value
thermal.tzp= [HW,ACPI]
Specify global default ACPI thermal zone polling rate
<deci-seconds>: poll all this frequency
0: no polling (default)
threadirqs [KNL]
Force threading of all interrupt handlers except those
marked explicitly IRQF_NO_THREAD.
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tmem [KNL,XEN]
Enable the Transcendent memory driver if built-in.
tmem.cleancache=0|1 [KNL, XEN]
Default is on (1). Disable the usage of the cleancache
API to send anonymous pages to the hypervisor.
tmem.frontswap=0|1 [KNL, XEN]
Default is on (1). Disable the usage of the frontswap
API to send swap pages to the hypervisor. If disabled
the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk
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tmem.selfballooning=0|1 [KNL, XEN]
Default is on (1). Disable the driving of swap pages
to the hypervisor.
tmem.selfshrinking=0|1 [KNL, XEN]
Default is on (1). Partial swapoff that immediately
transfers pages from Xen hypervisor back to the
kernel based on different criteria.
topology= [S390]
Format: {off | on}
Specify if the kernel should make use of the cpu
topology information if the hardware supports this.
The scheduler will make use of this information and
e.g. base its process migration decisions on it.
tpm_suspend_pcr=[HW,TPM]
Format: integer pcr id
Specify that at suspend time, the tpm driver
should extend the specified pcr with zeros,
as a workaround for some chips which fail to
flush the last written pcr on TPM_SaveState.
This will guarantee that all the other pcrs
are saved.
trace_buf_size=nn[KMG]
[FTRACE] will set tracing buffer size.
trace_event=[event-list]
[FTRACE] Set and start specified trace events in order
to facilitate early boot debugging.
See also Documentation/trace/events.txt
trace_options=[option-list]
[FTRACE] Enable or disable tracer options at boot.
The option-list is a comma delimited list of options
that can be enabled or disabled just as if you were
to echo the option name into
/sys/kernel/debug/tracing/trace_options
For example, to enable stacktrace option (to dump the
stack trace of each event), add to the command line:
trace_options=stacktrace
See also Documentation/trace/ftrace.txt "trace options"
section.
traceoff_on_warning
[FTRACE] enable this option to disable tracing when a
warning is hit. This turns off "tracing_on". Tracing can
be enabled again by echoing '1' into the "tracing_on"
file located in /sys/kernel/debug/tracing/
This option is useful, as it disables the trace before
the WARNING dump is called, which prevents the trace to
be filled with content caused by the warning output.
This option can also be set at run time via the sysctl
option: kernel/traceoff_on_warning
transparent_hugepage=
[KNL]
Format: [always|madvise|never]
Can be used to control the default behavior of the system
with respect to transparent hugepages.
See Documentation/vm/transhuge.txt for more details.
tsc= Disable clocksource stability checks for TSC.
Format: <string>
[x86] reliable: mark tsc clocksource as reliable, this
disables clocksource verification at runtime, as well
as the stability checks done at bootup. Used to enable
high-resolution timer mode on older hardware, and in
virtualized environment.
[x86] noirqtime: Do not use TSC to do irq accounting.
Used to run time disable IRQ_TIME_ACCOUNTING on any
platforms where RDTSC is slow and this accounting
can add overhead.
turbografx.map[2|3]= [HW,JOY]
TurboGraFX parallel port interface
Format:
<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
See also Documentation/input/joystick-parport.txt
udbg-immortal [PPC] When debugging early kernel crashes that
happen after console_init() and before a proper
console driver takes over, this boot options might
help "seeing" what's going on.
uhash_entries= [KNL,NET]
Set number of hash buckets for UDP/UDP-Lite connections
uhci-hcd.ignore_oc=
[USB] Ignore overcurrent events (default N).
Some badly-designed motherboards generate lots of
bogus events, for ports that aren't wired to
anything. Set this parameter to avoid log spamming.
Note that genuine overcurrent events won't be
reported either.
[X86] Cause panic on unknown NMI.
usbcore.authorized_default=
[USB] Default USB device authorization:
(default -1 = authorized except for wireless USB,
0 = not authorized, 1 = authorized)
usbcore.autosuspend=
[USB] The autosuspend time delay (in seconds) used
for newly-detected USB devices (default 2). This
is the time required before an idle device will be
autosuspended. Devices for which the delay is set
to a negative value won't be autosuspended at all.
usbcore.usbfs_snoop=
[USB] Set to log all usbfs traffic (default 0 = off).
usbcore.blinkenlights=
[USB] Set to cycle leds on hubs (default 0 = off).
usbcore.old_scheme_first=
[USB] Start with the old device initialization
scheme (default 0 = off).
usbcore.usbfs_memory_mb=
[USB] Memory limit (in MB) for buffers allocated by
usbfs (default = 16, 0 = max = 2047).
usbcore.use_both_schemes=
[USB] Try the other device initialization scheme
if the first one fails (default 1 = enabled).
usbcore.initial_descriptor_timeout=
[USB] Specifies timeout for the initial 64-byte
USB_REQ_GET_DESCRIPTOR request in milliseconds
(default 5000 = 5.0 seconds).
usbhid.mousepoll=
[USBHID] The interval which mice are to be polled at.
usb-storage.delay_use=
[UMS] The delay in seconds before a new device is
scanned for Logical Units (default 5).
usb-storage.quirks=
[UMS] A list of quirks entries to supplement or
override the built-in unusual_devs list. List
entries are separated by commas. Each entry has
the form VID:PID:Flags where VID and PID are Vendor
and Product ID values (4-digit hex numbers) and
Flags is a set of characters, each corresponding
to a common usb-storage quirk flag as follows:
a = SANE_SENSE (collect more than 18 bytes
of sense data);
b = BAD_SENSE (don't collect more than 18
bytes of sense data);
c = FIX_CAPACITY (decrease the reported
device capacity by one sector);
d = NO_READ_DISC_INFO (don't use
READ_DISC_INFO command);
e = NO_READ_CAPACITY_16 (don't use
READ_CAPACITY_16 command);
h = CAPACITY_HEURISTICS (decrease the
reported device capacity by one
sector if the number is odd);
i = IGNORE_DEVICE (don't bind to this
device);
l = NOT_LOCKABLE (don't try to lock and
unlock ejectable media);
m = MAX_SECTORS_64 (don't transfer more
than 64 sectors = 32 KB at a time);
n = INITIAL_READ10 (force a retry of the
initial READ(10) command);
o = CAPACITY_OK (accept the capacity
reported by the device);
p = WRITE_CACHE (the device cache is ON
by default);
r = IGNORE_RESIDUE (the device reports
bogus residue values);
s = SINGLE_LUN (the device has only one
Logical Unit);
w = NO_WP_DETECT (don't test whether the
medium is write-protected).
Example: quirks=0419:aaf5:rl,0421:0433:rc
user_debug= [KNL,ARM]
Format: <int>
See arch/arm/Kconfig.debug help text.
1 - undefined instruction events
2 - system calls
4 - invalid data aborts
8 - SIGSEGV faults
16 - SIGBUS faults
Example: user_debug=31
userpte=
[X86] Flags controlling user PTE allocations.
nohigh = do not allocate PTE pages in
HIGHMEM regardless of setting
of CONFIG_HIGHPTE.
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vdso= [X86,SH]
vdso=2: enable compat VDSO (default with COMPAT_VDSO)
vdso=1: enable VDSO (default)
vdso=0: disable VDSO mapping
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vdso32= [X86]
vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
vdso32=1: enable 32-bit VDSO (default)
vdso32=0: disable 32-bit VDSO mapping
vector= [IA-64,SMP]
vector=percpu: enable percpu vector domain
video= [FB] Frame buffer configuration
See Documentation/fb/modedb.txt.
video.brightness_switch_enabled= [0,1]
If set to 1, on receiving an ACPI notify event
generated by hotkey, video driver will adjust brightness
level and then send out the event to user space through
the allocated input device; If set to 0, video driver
will only send out the event without touching backlight
brightness level.
default: 1
virtio_mmio.device=
[VMMIO] Memory mapped virtio (platform) device.
<size>@<baseaddr>:<irq>[:<id>]
where:
<size> := size (can use standard suffixes
like K, M and G)
<baseaddr> := physical base address
<irq> := interrupt number (as passed to
request_irq())
<id> := (optional) platform device id
example:
virtio_mmio.device=1K@0x100b0000:48:7
Can be used multiple times for multiple devices.
vga= [BOOT,X86-32] Select a particular video mode
See Documentation/x86/boot.txt and
Use vga=ask for menu.
This is actually a boot loader parameter; the value is
passed to the kernel using a special protocol.
vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
size of <nn>. This can be used to increase the
minimum size (128MB on x86). It can also be used to
decrease the size and leave more room for directly
mapped kernel RAM.
vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
Format: <command>
vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
Format: <command>
vmpoff= [KNL,S390] Perform z/VM CP command after power off.
Format: <command>
vsyscall= [X86-64]
Controls the behavior of vsyscalls (i.e. calls to
fixed addresses of 0xffffffffff600x00 from legacy
code). Most statically-linked binaries and older
versions of glibc use these calls. Because these
functions are at fixed addresses, they make nice
targets for exploits that can control RIP.
emulate [default] Vsyscalls turn into traps and are
emulated reasonably safely.
native Vsyscalls are native syscall instructions.
This is a little bit faster than trapping
and makes a few dynamic recompilers work
better than they would in emulation mode.
It also makes exploits much easier to write.
none Vsyscalls don't work at all. This makes
them quite hard to use for exploits but
might break your system.
vt.color= [VT] Default text color.
Format: 0xYX, X = foreground, Y = background.
Default: 0x07 = light gray on black.
vt.cur_default= [VT] Default cursor shape.
Format: 0xCCBBAA, where AA, BB, and CC are the same as
the parameters of the <Esc>[?A;B;Cc escape sequence;
see VGA-softcursor.txt. Default: 2 = underline.
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vt.default_blu= [VT]
Format: <blue0>,<blue1>,<blue2>,...,<blue15>
Change the default blue palette of the console.
This is a 16-member array composed of values
ranging from 0-255.
vt.default_grn= [VT]
Format: <green0>,<green1>,<green2>,...,<green15>
Change the default green palette of the console.
This is a 16-member array composed of values
ranging from 0-255.
vt.default_red= [VT]
Format: <red0>,<red1>,<red2>,...,<red15>
Change the default red palette of the console.
This is a 16-member array composed of values
ranging from 0-255.
vt.default_utf8=
[VT]
Format=<0|1>
Set system-wide default UTF-8 mode for all tty's.
Default is 1, i.e. UTF-8 mode is enabled for all
newly opened terminals.
vt.global_cursor_default=
[VT]
Format=<-1|0|1>
Set system-wide default for whether a cursor
is shown on new VTs. Default is -1,
i.e. cursors will be created by default unless
overridden by individual drivers. 0 will hide
cursors, 1 will display them.
vt.italic= [VT] Default color for italic text; 0-15.
Default: 2 = green.
vt.underline= [VT] Default color for underlined text; 0-15.
Default: 3 = cyan.
watchdog timers [HW,WDT] For information on watchdog timers,
see Documentation/watchdog/watchdog-parameters.txt
or other driver-specific files in the
Documentation/watchdog/ directory.
Tejun Heo
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workqueue.disable_numa
By default, all work items queued to unbound
workqueues are affine to the NUMA nodes they're
issued on, which results in better behavior in
general. If NUMA affinity needs to be disabled for
whatever reason, this option can be used. Note
that this also can be controlled per-workqueue for
workqueues visible under /sys/bus/workqueue/.
Viresh Kumar
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workqueue.power_efficient
Per-cpu workqueues are generally preferred because
they show better performance thanks to cache
locality; unfortunately, per-cpu workqueues tend to
be more power hungry than unbound workqueues.
Enabling this makes the per-cpu workqueues which
were observed to contribute significantly to power
consumption unbound, leading to measurably lower
power usage at the cost of small performance
overhead.
The default value of this parameter is determined by
the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
default x2apic cluster mode on platforms
supporting x2apic.
x86_intel_mid_timer= [X86-32,APBT]
Choose timer option for x86 Intel MID platform.
Two valid options are apbt timer only and lapic timer
plus one apbt timer for broadcast timer.
x86_intel_mid_timer=apbt_only | lapic_and_apbt
xen_emul_unplug= [HW,X86,XEN]
Unplug Xen emulated devices
Format: [unplug0,][unplug1]
ide-disks -- unplug primary master IDE devices
aux-ide-disks -- unplug non-primary-master IDE devices
nics -- unplug network devices
all -- unplug all emulated devices (NICs and IDE disks)
unnecessary -- unplugging emulated devices is
unnecessary even if the host did not respond to
the unplug protocol
never -- do not unplug even if version check succeeds
xen_nopvspin [X86,XEN]
Disables the ticketlock slowpath using Xen PV
optimizations.
Format:
<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
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