and vice versa. See <file:Documentation/sgi-visws.txt> for details.
config X86_GENERICARCH
- bool "Generic architecture (Summit, bigsmp, default)"
+ bool "Generic architecture (Summit, bigsmp, ES7000, default)"
depends on SMP
help
- This option compiles in the Summit, bigsmp, default subarchitectures.
+ This option compiles in the Summit, bigsmp, ES7000, default subarchitectures.
It is intended for a generic binary kernel.
config X86_ES7000
depends on (MWINCHIP3D || MWINCHIP2 || MWINCHIPC6) && MTRR
default y
+config X86_4G
+ bool "4 GB kernel-space and 4 GB user-space virtual memory support"
+ help
+ This option is only useful for systems that have more than 1 GB
+ of RAM.
+
+ The default kernel VM layout leaves 1 GB of virtual memory for
+ kernel-space mappings, and 3 GB of VM for user-space applications.
+ This option ups both the kernel-space VM and the user-space VM to
+ 4 GB.
+
+ The cost of this option is additional TLB flushes done at
+ system-entry points that transition from user-mode into kernel-mode.
+ I.e. system calls and page faults, and IRQs that interrupt user-mode
+ code. There's also additional overhead to kernel operations that copy
+ memory to/from user-space. The overhead from this is hard to tell and
+ depends on the workload - it can be anything from no visible overhead
+ to 20-30% overhead. A good rule of thumb is to count with a runtime
+ overhead of 20%.
+
+ The upside is the much increased kernel-space VM, which more than
+ quadruples the maximum amount of RAM supported. Kernels compiled with
+ this option boot on 64GB of RAM and still have more than 3.1 GB of
+ 'lowmem' left. Another bonus is that highmem IO bouncing decreases,
+ if used with drivers that still use bounce-buffers.
+
+ There's also a 33% increase in user-space VM size - database
+ applications might see a boost from this.
+
+ But the cost of the TLB flushes and the runtime overhead has to be
+ weighed against the bonuses offered by the larger VM spaces. The
+ dividing line depends on the actual workload - there might be 4 GB
+ systems that benefit from this option. Systems with less than 4 GB
+ of RAM will rarely see a benefit from this option - but it's not
+ out of question, the exact circumstances have to be considered.
+
+config X86_SWITCH_PAGETABLES
+ def_bool X86_4G
+
+config X86_4G_VM_LAYOUT
+ def_bool X86_4G
+
+config X86_UACCESS_INDIRECT
+ def_bool X86_4G
+
+config X86_HIGH_ENTRY
+ def_bool X86_4G
+
config HPET_TIMER
bool "HPET Timer Support"
help
This is purely to save memory - each supported CPU adds
approximately eight kilobytes to the kernel image.
+config SCHED_SMT
+ bool "SMT (Hyperthreading) scheduler support"
+ depends on SMP
+ default off
+ help
+ SMT scheduler support improves the CPU scheduler's decision making
+ when dealing with Intel Pentium 4 chips with HyperThreading at a
+ cost of slightly increased overhead in some places. If unsure say
+ N here.
+
config PREEMPT
bool "Preemptible Kernel"
help
# Common NUMA Features
config NUMA
- bool "Numa Memory Allocation Support"
+ bool "Numa Memory Allocation and Scheduler Support"
depends on SMP && HIGHMEM64G && (X86_NUMAQ || X86_GENERICARCH || (X86_SUMMIT && ACPI))
default n if X86_PC
default y if (X86_NUMAQ || X86_SUMMIT)
If you don't debug the kernel, you can say N, but we may not be able
to solve problems without frame pointers.
-config 4KSTACKS
- bool "Use 4Kb for kernel stacks instead of 8Kb"
- help
- If you say Y here the kernel will use a 4Kb stacksize for the
- kernel stack attached to each process/thread. This facilitates
- running more threads on a system and also reduces the pressure
- on the VM subsystem for higher order allocations. This option
- will also use IRQ stacks to compensate for the reduced stackspace.
-
config X86_FIND_SMP_CONFIG
bool
depends on X86_LOCAL_APIC || X86_VOYAGER
git://git.onelab.eu / linux-2.6.git / blobdiff