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linux/arch/frv/Kconfig
Christoph Lameter 81819f0fc8 SLUB core 
This is a new slab allocator which was motivated by the complexity of the
existing code in mm/slab.c. It attempts to address a variety of concerns
with the existing implementation.

A. Management of object queues

   A particular concern was the complex management of the numerous object
   queues in SLAB. SLUB has no such queues. Instead we dedicate a slab for
   each allocating CPU and use objects from a slab directly instead of
   queueing them up.

B. Storage overhead of object queues

   SLAB Object queues exist per node, per CPU. The alien cache queue even
   has a queue array that contain a queue for each processor on each
   node. For very large systems the number of queues and the number of
   objects that may be caught in those queues grows exponentially. On our
   systems with 1k nodes / processors we have several gigabytes just tied up
   for storing references to objects for those queues  This does not include
   the objects that could be on those queues. One fears that the whole
   memory of the machine could one day be consumed by those queues.

C. SLAB meta data overhead

   SLAB has overhead at the beginning of each slab. This means that data
   cannot be naturally aligned at the beginning of a slab block. SLUB keeps
   all meta data in the corresponding page_struct. Objects can be naturally
   aligned in the slab. F.e. a 128 byte object will be aligned at 128 byte
   boundaries and can fit tightly into a 4k page with no bytes left over.
   SLAB cannot do this.

D. SLAB has a complex cache reaper

   SLUB does not need a cache reaper for UP systems. On SMP systems
   the per CPU slab may be pushed back into partial list but that
   operation is simple and does not require an iteration over a list
   of objects. SLAB expires per CPU, shared and alien object queues
   during cache reaping which may cause strange hold offs.

E. SLAB has complex NUMA policy layer support

   SLUB pushes NUMA policy handling into the page allocator. This means that
   allocation is coarser (SLUB does interleave on a page level) but that
   situation was also present before 2.6.13. SLABs application of
   policies to individual slab objects allocated in SLAB is
   certainly a performance concern due to the frequent references to
   memory policies which may lead a sequence of objects to come from
   one node after another. SLUB will get a slab full of objects
   from one node and then will switch to the next.

F. Reduction of the size of partial slab lists

   SLAB has per node partial lists. This means that over time a large
   number of partial slabs may accumulate on those lists. These can
   only be reused if allocator occur on specific nodes. SLUB has a global
   pool of partial slabs and will consume slabs from that pool to
   decrease fragmentation.

G. Tunables

   SLAB has sophisticated tuning abilities for each slab cache. One can
   manipulate the queue sizes in detail. However, filling the queues still
   requires the uses of the spin lock to check out slabs. SLUB has a global
   parameter (min_slab_order) for tuning. Increasing the minimum slab
   order can decrease the locking overhead. The bigger the slab order the
   less motions of pages between per CPU and partial lists occur and the
   better SLUB will be scaling.

G. Slab merging

   We often have slab caches with similar parameters. SLUB detects those
   on boot up and merges them into the corresponding general caches. This
   leads to more effective memory use. About 50% of all caches can
   be eliminated through slab merging. This will also decrease
   slab fragmentation because partial allocated slabs can be filled
   up again. Slab merging can be switched off by specifying
   slub_nomerge on boot up.

   Note that merging can expose heretofore unknown bugs in the kernel
   because corrupted objects may now be placed differently and corrupt
   differing neighboring objects. Enable sanity checks to find those.

H. Diagnostics

   The current slab diagnostics are difficult to use and require a
   recompilation of the kernel. SLUB contains debugging code that
   is always available (but is kept out of the hot code paths).
   SLUB diagnostics can be enabled via the "slab_debug" option.
   Parameters can be specified to select a single or a group of
   slab caches for diagnostics. This means that the system is running
   with the usual performance and it is much more likely that
   race conditions can be reproduced.

I. Resiliency

   If basic sanity checks are on then SLUB is capable of detecting
   common error conditions and recover as best as possible to allow the
   system to continue.

J. Tracing

   Tracing can be enabled via the slab_debug=T,<slabcache> option
   during boot. SLUB will then protocol all actions on that slabcache
   and dump the object contents on free.

K. On demand DMA cache creation.

   Generally DMA caches are not needed. If a kmalloc is used with
   __GFP_DMA then just create this single slabcache that is needed.
   For systems that have no ZONE_DMA requirement the support is
   completely eliminated.

L. Performance increase

   Some benchmarks have shown speed improvements on kernbench in the
   range of 5-10%. The locking overhead of slub is based on the
   underlying base allocation size. If we can reliably allocate
   larger order pages then it is possible to increase slub
   performance much further. The anti-fragmentation patches may
   enable further performance increases.

Tested on:
i386 UP + SMP, x86_64 UP + SMP + NUMA emulation, IA64 NUMA + Simulator

SLUB Boot options

slub_nomerge		Disable merging of slabs
slub_min_order=x	Require a minimum order for slab caches. This
			increases the managed chunk size and therefore
			reduces meta data and locking overhead.
slub_min_objects=x	Mininum objects per slab. Default is 8.
slub_max_order=x	Avoid generating slabs larger than order specified.
slub_debug		Enable all diagnostics for all caches
slub_debug=<options>	Enable selective options for all caches
slub_debug=<o>,<cache>	Enable selective options for a certain set of
			caches

Available Debug options
F		Double Free checking, sanity and resiliency
R		Red zoning
P		Object / padding poisoning
U		Track last free / alloc
T		Trace all allocs / frees (only use for individual slabs).

To use SLUB: Apply this patch and then select SLUB as the default slab
allocator.

[hugh@veritas.com: fix an oops-causing locking error]
[akpm@linux-foundation.org: various stupid cleanups and small fixes]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-07 12:12:53 -07:00

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#
# For a description of the syntax of this configuration file,
# see Documentation/kbuild/kconfig-language.txt.
#
config FRV
bool
default y
config ZONE_DMA
bool
default y
config RWSEM_GENERIC_SPINLOCK
bool
default y
config RWSEM_XCHGADD_ALGORITHM
bool
config GENERIC_FIND_NEXT_BIT
bool
default y
config GENERIC_HWEIGHT
bool
default y
config GENERIC_CALIBRATE_DELAY
bool
default n
config GENERIC_HARDIRQS
bool
default y
config GENERIC_HARDIRQS_NO__DO_IRQ
bool
default y
config GENERIC_TIME
bool
default y
config TIME_LOW_RES
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default y
config ARCH_HAS_ILOG2_U64
bool
default y
config ARCH_USES_SLAB_PAGE_STRUCT
bool
default y
mainmenu "Fujitsu FR-V Kernel Configuration"
source "init/Kconfig"
menu "Fujitsu FR-V system setup"
config MMU
bool "MMU support"
help
This options switches on and off support for the FR-V MMU
(effectively switching between vmlinux and uClinux). Not all FR-V
CPUs support this. Currently only the FR451 has a sufficiently
featured MMU.
config FRV_OUTOFLINE_ATOMIC_OPS
bool "Out-of-line the FRV atomic operations"
default n
help
Setting this option causes the FR-V atomic operations to be mostly
implemented out-of-line.
See Documentation/fujitsu/frv/atomic-ops.txt for more information.
config HIGHMEM
bool "High memory support"
depends on MMU
default y
help
If you wish to use more than 256MB of memory with your MMU based
system, you will need to select this option. The kernel can only see
the memory between 0xC0000000 and 0xD0000000 directly... everything
else must be kmapped.
The arch is, however, capable of supporting up to 3GB of SDRAM.
config HIGHPTE
bool "Allocate page tables in highmem"
depends on HIGHMEM
default y
help
The VM uses one page of memory for each page table. For systems
with a lot of RAM, this can be wasteful of precious low memory.
Setting this option will put user-space page tables in high memory.
config LARGE_ALLOCS
bool "Allow allocating large blocks (> 1MB) of memory"
help
Allow the slab memory allocator to keep chains for very large memory
sizes - up to 32MB. You may need this if your system has a lot of
RAM, and you need to able to allocate very large contiguous chunks.
If unsure, say N.
source "mm/Kconfig"
choice
prompt "uClinux kernel load address"
depends on !MMU
default UCPAGE_OFFSET_C0000000
help
This option sets the base address for the uClinux kernel. The kernel
will rearrange the SDRAM layout to start at this address, and move
itself to start there. It must be greater than 0, and it must be
sufficiently less than 0xE0000000 that the SDRAM does not intersect
the I/O region.
The base address must also be aligned such that the SDRAM controller
can decode it. For instance, a 512MB SDRAM bank must be 512MB aligned.
config UCPAGE_OFFSET_20000000
bool "0x20000000"
config UCPAGE_OFFSET_40000000
bool "0x40000000"
config UCPAGE_OFFSET_60000000
bool "0x60000000"
config UCPAGE_OFFSET_80000000
bool "0x80000000"
config UCPAGE_OFFSET_A0000000
bool "0xA0000000"
config UCPAGE_OFFSET_C0000000
bool "0xC0000000 (Recommended)"
endchoice
config PROTECT_KERNEL
bool "Protect core kernel against userspace"
depends on !MMU
default y
help
Selecting this option causes the uClinux kernel to change the
permittivity of DAMPR register covering the core kernel image to
prevent userspace accessing the underlying memory directly.
choice
prompt "CPU Caching mode"
default FRV_DEFL_CACHE_WBACK
help
This option determines the default caching mode for the kernel.
Write-Back caching mode involves the all reads and writes causing
the affected cacheline to be read into the cache first before being
operated upon. Memory is not then updated by a write until the cache
is filled and a cacheline needs to be displaced from the cache to
make room. Only at that point is it written back.
Write-Behind caching is similar to Write-Back caching, except that a
write won't fetch a cacheline into the cache if there isn't already
one there; it will write directly to memory instead.
Write-Through caching only fetches cachelines from memory on a
read. Writes always get written directly to memory. If the affected
cacheline is also in cache, it will be updated too.
The final option is to turn of caching entirely.
Note that not all CPUs support Write-Behind caching. If the CPU on
which the kernel is running doesn't, it'll fall back to Write-Back
caching.
config FRV_DEFL_CACHE_WBACK
bool "Write-Back"
config FRV_DEFL_CACHE_WBEHIND
bool "Write-Behind"
config FRV_DEFL_CACHE_WTHRU
bool "Write-Through"
config FRV_DEFL_CACHE_DISABLED
bool "Disabled"
endchoice
menu "CPU core support"
config CPU_FR401
bool "Include FR401 core support"
depends on !MMU
default y
help
This enables support for the FR401, FR401A and FR403 CPUs
config CPU_FR405
bool "Include FR405 core support"
depends on !MMU
default y
help
This enables support for the FR405 CPU
config CPU_FR451
bool "Include FR451 core support"
default y
help
This enables support for the FR451 CPU
config CPU_FR451_COMPILE
bool "Specifically compile for FR451 core"
depends on CPU_FR451 && !CPU_FR401 && !CPU_FR405 && !CPU_FR551
default y
help
This causes appropriate flags to be passed to the compiler to
optimise for the FR451 CPU
config CPU_FR551
bool "Include FR551 core support"
depends on !MMU
default y
help
This enables support for the FR555 CPU
config CPU_FR551_COMPILE
bool "Specifically compile for FR551 core"
depends on CPU_FR551 && !CPU_FR401 && !CPU_FR405 && !CPU_FR451
default y
help
This causes appropriate flags to be passed to the compiler to
optimise for the FR555 CPU
config FRV_L1_CACHE_SHIFT
int
default "5" if CPU_FR401 || CPU_FR405 || CPU_FR451
default "6" if CPU_FR551
endmenu
choice
prompt "System support"
default MB93091_VDK
config MB93091_VDK
bool "MB93091 CPU board with or without motherboard"
config MB93093_PDK
bool "MB93093 PDK unit"
endchoice
if MB93091_VDK
choice
prompt "Motherboard support"
default MB93090_MB00
config MB93090_MB00
bool "Use the MB93090-MB00 motherboard"
help
Select this option if the MB93091 CPU board is going to be used with
a MB93090-MB00 VDK motherboard
config MB93091_NO_MB
bool "Use standalone"
help
Select this option if the MB93091 CPU board is going to be used
without a motherboard
endchoice
endif
config FUJITSU_MB93493
bool "MB93493 Multimedia chip"
help
Select this option if the MB93493 multimedia chip is going to be
used.
choice
prompt "GP-Relative data support"
default GPREL_DATA_8
help
This option controls what data, if any, should be placed in the GP
relative data sections. Using this means that the compiler can
generate accesses to the data using GR16-relative addressing which
is faster than absolute instructions and saves space (2 instructions
per access).
However, the GPREL region is limited in size because the immediate
value used in the load and store instructions is limited to a 12-bit
signed number.
So if the linker starts complaining that accesses to GPREL data are
out of range, try changing this option from the default.
Note that modules will always be compiled with this feature disabled
as the module data will not be in range of the GP base address.
config GPREL_DATA_8
bool "Put data objects of up to 8 bytes into GP-REL"
config GPREL_DATA_4
bool "Put data objects of up to 4 bytes into GP-REL"
config GPREL_DATA_NONE
bool "Don't use GP-REL"
endchoice
config FRV_ONCPU_SERIAL
bool "Use on-CPU serial ports"
select SERIAL_8250
default y
config PCI
bool "Use PCI"
depends on MB93090_MB00
default y
help
Some FR-V systems (such as the MB93090-MB00 VDK) have PCI
onboard. If you have one of these boards and you wish to use the PCI
facilities, say Y here.
The PCI-HOWTO, available from
<http://www.tldp.org/docs.html#howto>, contains valuable
information about which PCI hardware does work under Linux and which
doesn't.
config RESERVE_DMA_COHERENT
bool "Reserve DMA coherent memory"
depends on PCI && !MMU
default y
help
Many PCI drivers require access to uncached memory for DMA device
communications (such as is done with some Ethernet buffer rings). If
a fully featured MMU is available, this can be done through page
table settings, but if not, a region has to be set aside and marked
with a special DAMPR register.
Setting this option causes uClinux to set aside a portion of the
available memory for use in this manner. The memory will then be
unavailable for normal kernel use.
source "drivers/pci/Kconfig"
source "drivers/pcmcia/Kconfig"
#config MATH_EMULATION
# bool "Math emulation support (EXPERIMENTAL)"
# depends on EXPERIMENTAL
# help
# At some point in the future, this will cause floating-point math
# instructions to be emulated by the kernel on machines that lack a
# floating-point math coprocessor. Thrill-seekers and chronically
# sleep-deprived psychotic hacker types can say Y now, everyone else
# should probably wait a while.
menu "Power management options"
source kernel/power/Kconfig
endmenu
endmenu
menu "Executable formats"
source "fs/Kconfig.binfmt"
endmenu
source "net/Kconfig"
source "drivers/Kconfig"
source "fs/Kconfig"
source "arch/frv/Kconfig.debug"
source "security/Kconfig"
source "crypto/Kconfig"
source "lib/Kconfig"
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