loops can be debugged more effectively on production
systems.
- clearcpuid=BITNUM [X86]
+ clearcpuid=BITNUM[,BITNUM...] [X86]
Disable CPUID feature X for the kernel. See
arch/x86/include/asm/cpufeatures.h for the valid bit
numbers. Note the Linux specific bits are not necessarily
some critical bits.
cma=nn[MG]@[start[MG][-end[MG]]]
- [ARM,X86,KNL]
+ [KNL,CMA]
Sets the size of kernel global memory area for
contiguous memory allocations and optionally the
placement constraint by the physical address range of
memory allocations. A value of 0 disables CMA
altogether. For more information, see
- include/linux/dma-contiguous.h
+ kernel/dma/contiguous.c
+
+ cma_pernuma=nn[MG]
+ [ARM64,KNL]
+ Sets the size of kernel per-numa memory area for
+ contiguous memory allocations. A value of 0 disables
+ per-numa CMA altogether. And If this option is not
+ specificed, the default value is 0.
+ With per-numa CMA enabled, DMA users on node nid will
+ first try to allocate buffer from the pernuma area
+ which is located in node nid, if the allocation fails,
+ they will fallback to the global default memory area.
cmo_free_hint= [PPC] Format: { yes | no }
Specify whether pages are marked as being inactive
Arch Perfmon v4 (Skylake and newer).
disable_ddw [PPC/PSERIES]
- Disable Dynamic DMA Window support. Use this if
+ Disable Dynamic DMA Window support. Use this
to workaround buggy firmware.
disable_ipv6= [IPV6]
what data is available or for reverse-engineering.
dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
- module.dyndbg[="val"]
+ <module>.dyndbg[="val"]
Enable debug messages at boot time. See
Documentation/admin-guide/dynamic-debug-howto.rst
for details.
nopku [X86] Disable Memory Protection Keys CPU feature found
in some Intel CPUs.
- module.async_probe [KNL]
+ <module>.async_probe [KNL]
Enable asynchronous probe on this module.
early_ioremap_debug [KNL]
current integrity status.
failslab=
+ fail_usercopy=
fail_page_alloc=
fail_make_request=[KNL]
General fault injection mechanism.
Format: <interval>,<probability>,<space>,<times>
See also Documentation/fault-injection/.
+ fb_tunnels= [NET]
+ Format: { initns | none }
+ See Documentation/admin-guide/sysctl/net.rst for
+ fb_tunnels_only_for_init_ns
+
floppy= [HW]
See Documentation/admin-guide/blockdev/floppy.rst.
1 - Bypass the IOMMU for DMA.
unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
- io7= [HW] IO7 for Marvel based alpha systems
+ io7= [HW] IO7 for Marvel-based Alpha systems
See comment before marvel_specify_io7 in
arch/alpha/kernel/core_marvel.c.
kgdbwait [KGDB] Stop kernel execution and enter the
kernel debugger at the earliest opportunity.
- kmac= [MIPS] korina ethernet MAC address.
+ kmac= [MIPS] Korina ethernet MAC address.
Configure the RouterBoard 532 series on-chip
Ethernet adapter MAC address.
[KVM,ARM] Allow use of GICv4 for direct injection of
LPIs.
+ kvm_cma_resv_ratio=n [PPC]
+ Reserves given percentage from system memory area for
+ contiguous memory allocation for KVM hash pagetable
+ allocation.
+ By default it reserves 5% of total system memory.
+ Format: <integer>
+ Default: 5
+
kvm-intel.ept= [KVM,Intel] Disable extended page tables
(virtualized MMU) support on capable Intel chips.
Default is 1 (enabled)
lapic [X86-32,APIC] Enable the local APIC even if BIOS
disabled it.
- lapic= [X86,APIC] "notscdeadline" Do not use TSC deadline
+ lapic= [X86,APIC] Do not use TSC deadline
value for LAPIC timer one-shot implementation. Default
back to the programmable timer unit in the LAPIC.
+ Format: notscdeadline
lapic_timer_c2_ok [X86,APIC] trust the local apic timer
in C2 power state.
memblock=debug [KNL] Enable memblock debug messages.
- load_ramdisk= [RAM] List of ramdisks to load from floppy
- See Documentation/admin-guide/blockdev/ramdisk.rst.
+ load_ramdisk= [RAM] [Deprecated]
lockd.nlm_grace_period=P [NFS] Assign grace period.
Format: <integer>
(machvec) in a generic kernel.
Example: machvec=hpzx1
- machtype= [Loongson] Share the same kernel image file between different
- yeeloong laptop.
+ machtype= [Loongson] Share the same kernel image file between
+ different yeeloong laptops.
Example: machtype=lemote-yeeloong-2f-7inch
max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
and gids from such clients. This is intended to ease
migration from NFSv2/v3.
+ nmi_backtrace.backtrace_idle [KNL]
+ Dump stacks even of idle CPUs in response to an
+ NMI stack-backtrace request.
+
nmi_debug= [KNL,SH] Specify one or more actions to take
when a NMI is triggered.
Format: [state][,regs][,debounce][,die]
register save and restore. The kernel will only save
legacy floating-point registers on task switch.
- nohugeiomap [KNL,X86,PPC] Disable kernel huge I/O mappings.
+ nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
nosmt [KNL,S390] Disable symmetric multithreading (SMT).
Equivalent to smt=1.
Param: <number> - step/bucket size as a power of 2 for
statistical time based profiling.
- prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
- before loading.
- See Documentation/admin-guide/blockdev/ramdisk.rst.
+ prompt_ramdisk= [RAM] [Deprecated]
prot_virt= [S390] enable hosting protected virtual machines
isolated from the hypervisor (if hardware supports
ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
See Documentation/admin-guide/blockdev/ramdisk.rst.
+ ramdisk_start= [RAM] RAM disk image start address
+
random.trust_cpu={on,off}
[KNL] Enable or disable trusting the use of the
CPU's random number generator (if available) to
This wake_up() will be accompanied by a
WARN_ONCE() splat and an ftrace_dump().
+ rcutree.rcu_unlock_delay= [KNL]
+ In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
+ this specifies an rcu_read_unlock()-time delay
+ in microseconds. This defaults to zero.
+ Larger delays increase the probability of
+ catching RCU pointer leaks, that is, buggy use
+ of RCU-protected pointers after the relevant
+ rcu_read_unlock() has completed.
+
rcutree.sysrq_rcu= [KNL]
Commandeer a sysrq key to dump out Tree RCU's
rcu_node tree with an eye towards determining
why a new grace period has not yet started.
- rcuperf.gp_async= [KNL]
+ rcuscale.gp_async= [KNL]
Measure performance of asynchronous
grace-period primitives such as call_rcu().
- rcuperf.gp_async_max= [KNL]
+ rcuscale.gp_async_max= [KNL]
Specify the maximum number of outstanding
callbacks per writer thread. When a writer
thread exceeds this limit, it invokes the
corresponding flavor of rcu_barrier() to allow
previously posted callbacks to drain.
- rcuperf.gp_exp= [KNL]
+ rcuscale.gp_exp= [KNL]
Measure performance of expedited synchronous
grace-period primitives.
- rcuperf.holdoff= [KNL]
+ rcuscale.holdoff= [KNL]
Set test-start holdoff period. The purpose of
this parameter is to delay the start of the
test until boot completes in order to avoid
interference.
- rcuperf.kfree_rcu_test= [KNL]
+ rcuscale.kfree_rcu_test= [KNL]
Set to measure performance of kfree_rcu() flooding.
- rcuperf.kfree_nthreads= [KNL]
+ rcuscale.kfree_nthreads= [KNL]
The number of threads running loops of kfree_rcu().
- rcuperf.kfree_alloc_num= [KNL]
+ rcuscale.kfree_alloc_num= [KNL]
Number of allocations and frees done in an iteration.
- rcuperf.kfree_loops= [KNL]
- Number of loops doing rcuperf.kfree_alloc_num number
+ rcuscale.kfree_loops= [KNL]
+ Number of loops doing rcuscale.kfree_alloc_num number
of allocations and frees.
- rcuperf.nreaders= [KNL]
+ rcuscale.nreaders= [KNL]
Set number of RCU readers. The value -1 selects
N, where N is the number of CPUs. A value
"n" less than -1 selects N-n+1, where N is again
A value of "n" less than or equal to -N selects
a single reader.
- rcuperf.nwriters= [KNL]
+ rcuscale.nwriters= [KNL]
Set number of RCU writers. The values operate
- the same as for rcuperf.nreaders.
+ the same as for rcuscale.nreaders.
N, where N is the number of CPUs
- rcuperf.perf_type= [KNL]
+ rcuscale.perf_type= [KNL]
Specify the RCU implementation to test.
- rcuperf.shutdown= [KNL]
+ rcuscale.shutdown= [KNL]
Shut the system down after performance tests
complete. This is useful for hands-off automated
testing.
- rcuperf.verbose= [KNL]
+ rcuscale.verbose= [KNL]
Enable additional printk() statements.
- rcuperf.writer_holdoff= [KNL]
+ rcuscale.writer_holdoff= [KNL]
Write-side holdoff between grace periods,
in microseconds. The default of zero says
no holdoff.
are zero, rcutorture acts as if is interpreted
they are all non-zero.
+ rcutorture.irqreader= [KNL]
+ Run RCU readers from irq handlers, or, more
+ accurately, from a timer handler. Not all RCU
+ flavors take kindly to this sort of thing.
+
+ rcutorture.leakpointer= [KNL]
+ Leak an RCU-protected pointer out of the reader.
+ This can of course result in splats, and is
+ intended to test the ability of things like
+ CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
+ such leaks.
+
rcutorture.n_barrier_cbs= [KNL]
Set callbacks/threads for rcu_barrier() testing.
refscale.shutdown= [KNL]
Shut down the system at the end of the performance
test. This defaults to 1 (shut it down) when
- rcuperf is built into the kernel and to 0 (leave
- it running) when rcuperf is built as a module.
+ refscale is built into the kernel and to 0 (leave
+ it running) when refscale is built as a module.
refscale.verbose= [KNL]
Enable additional printk() statements.
Format: integer between 0 and 10
Default is 0.
+ scftorture.holdoff= [KNL]
+ Number of seconds to hold off before starting
+ test. Defaults to zero for module insertion and
+ to 10 seconds for built-in smp_call_function()
+ tests.
+
+ scftorture.longwait= [KNL]
+ Request ridiculously long waits randomly selected
+ up to the chosen limit in seconds. Zero (the
+ default) disables this feature. Please note
+ that requesting even small non-zero numbers of
+ seconds can result in RCU CPU stall warnings,
+ softlockup complaints, and so on.
+
+ scftorture.nthreads= [KNL]
+ Number of kthreads to spawn to invoke the
+ smp_call_function() family of functions.
+ The default of -1 specifies a number of kthreads
+ equal to the number of CPUs.
+
+ scftorture.onoff_holdoff= [KNL]
+ Number seconds to wait after the start of the
+ test before initiating CPU-hotplug operations.
+
+ scftorture.onoff_interval= [KNL]
+ Number seconds to wait between successive
+ CPU-hotplug operations. Specifying zero (which
+ is the default) disables CPU-hotplug operations.
+
+ scftorture.shutdown_secs= [KNL]
+ The number of seconds following the start of the
+ test after which to shut down the system. The
+ default of zero avoids shutting down the system.
+ Non-zero values are useful for automated tests.
+
+ scftorture.stat_interval= [KNL]
+ The number of seconds between outputting the
+ current test statistics to the console. A value
+ of zero disables statistics output.
+
+ scftorture.stutter_cpus= [KNL]
+ The number of jiffies to wait between each change
+ to the set of CPUs under test.
+
+ scftorture.use_cpus_read_lock= [KNL]
+ Use use_cpus_read_lock() instead of the default
+ preempt_disable() to disable CPU hotplug
+ while invoking one of the smp_call_function*()
+ functions.
+
+ scftorture.verbose= [KNL]
+ Enable additional printk() statements.
+
+ scftorture.weight_single= [KNL]
+ The probability weighting to use for the
+ smp_call_function_single() function with a zero
+ "wait" parameter. A value of -1 selects the
+ default if all other weights are -1. However,
+ if at least one weight has some other value, a
+ value of -1 will instead select a weight of zero.
+
+ scftorture.weight_single_wait= [KNL]
+ The probability weighting to use for the
+ smp_call_function_single() function with a
+ non-zero "wait" parameter. See weight_single.
+
+ scftorture.weight_many= [KNL]
+ The probability weighting to use for the
+ smp_call_function_many() function with a zero
+ "wait" parameter. See weight_single.
+ Note well that setting a high probability for
+ this weighting can place serious IPI load
+ on the system.
+
+ scftorture.weight_many_wait= [KNL]
+ The probability weighting to use for the
+ smp_call_function_many() function with a
+ non-zero "wait" parameter. See weight_single
+ and weight_many.
+
+ scftorture.weight_all= [KNL]
+ The probability weighting to use for the
+ smp_call_function_all() function with a zero
+ "wait" parameter. See weight_single and
+ weight_many.
+
+ scftorture.weight_all_wait= [KNL]
+ The probability weighting to use for the
+ smp_call_function_all() function with a
+ non-zero "wait" parameter. See weight_single
+ and weight_many.
+
skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
xtime_lock contention on larger systems, and/or RCU lock
contention on all systems with CONFIG_MAXSMP set.
After which time (jiffies) the event handling loop
should start to delay EOI handling. Default is 2.
+ xen.fifo_events= [XEN]
+ Boolean parameter to disable using fifo event handling
+ even if available. Normally fifo event handling is
+ preferred over the 2-level event handling, as it is
+ fairer and the number of possible event channels is
+ much higher. Default is on (use fifo events).
+
nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
Disables the PV optimizations forcing the guest to run
as generic guest with no PV drivers. Currently support
projects / J-linux.git / commitdiff