linux/arch/x86
Christoph Lameter 1f84260c8c SLUB: Alternate fast paths using cmpxchg_local
Provide an alternate implementation of the SLUB fast paths for alloc
and free using cmpxchg_local. The cmpxchg_local fast path is selected
for arches that have CONFIG_FAST_CMPXCHG_LOCAL set. An arch should only
set CONFIG_FAST_CMPXCHG_LOCAL if the cmpxchg_local is faster than an
interrupt enable/disable sequence. This is known to be true for both
x86 platforms so set FAST_CMPXCHG_LOCAL for both arches.

Currently another requirement for the fastpath is that the kernel is
compiled without preemption. The restriction will go away with the
introduction of a new per cpu allocator and new per cpu operations.

The advantages of a cmpxchg_local based fast path are:

1. Potentially lower cycle count (30%-60% faster)

2. There is no need to disable and enable interrupts on the fast path.
   Currently interrupts have to be disabled and enabled on every
   slab operation. This is likely avoiding a significant percentage
   of interrupt off / on sequences in the kernel.

3. The disposal of freed slabs can occur with interrupts enabled.

The alternate path is realized using #ifdef's. Several attempts to do the
same with macros and inline functions resulted in a mess (in particular due
to the strange way that local_interrupt_save() handles its argument and due
to the need to define macros/functions that sometimes disable interrupts
and sometimes do something else).

[clameter: Stripped preempt bits and disabled fastpath if preempt is enabled]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Reviewed-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2008-02-07 17:47:41 -08:00
..
boot x86: rename LARGE_PAGE_SIZE to PMD_PAGE_SIZE 2008-02-04 16:48:08 +01:00
configs x86: Set CFQ as default in 32-bit defconfig 2008-01-30 13:32:49 +01:00
crypto [CRYPTO] twofish: Merge common glue code 2008-01-14 17:07:57 +11:00
ia32 Sanitize the type of struct user.u_ar0 2008-02-07 08:42:30 -08:00
kernel Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 2008-02-07 09:45:58 -08:00
kvm kvm: i386 fix 2008-02-05 09:44:06 -08:00
lguest Merge git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus 2008-01-31 09:35:32 +11:00
lib read_current_timer() cleanups 2008-02-06 10:41:02 -08:00
mach-default spelling fixes: arch/i386/ 2007-10-20 01:13:56 +02:00
mach-es7000 i386: es7000 minor cleanups 2007-10-17 20:16:15 +02:00
mach-generic spelling fixes: arch/i386/ 2007-10-20 01:13:56 +02:00
mach-rdc321x x86: add support for the RDC R-321x SoC 2008-01-30 13:33:36 +01:00
mach-visws x86: cleanup mpspec variants 2008-01-30 13:30:35 +01:00
mach-voyager calibrate_delay() must be __cpuinit 2008-02-06 10:41:08 -08:00
math-emu x86: arch/x86/math-emu/errors.c: fix printk warnings 2008-01-30 13:32:13 +01:00
mm Introduce flags for reserve_bootmem() 2008-02-07 08:42:25 -08:00
oprofile x86: rename stack_pointer to kernel_trap_sp 2008-01-30 13:33:16 +01:00
pci intel-agp: add chipset flushing support 2008-02-05 14:33:32 +10:00
power x86: make __{save,restore}_processor_state static 2008-01-30 13:31:23 +01:00
vdso x86: add vdso32-int80-syms.lds to .gitignore 2008-01-30 13:33:24 +01:00
video
xen x86: return the page table level in lookup_address() 2008-01-30 13:33:43 +01:00
Kconfig SLUB: Alternate fast paths using cmpxchg_local 2008-02-07 17:47:41 -08:00
Kconfig.cpu x86: reduce CONFIG_X86_PPRO_FENCE bloat 2008-01-30 13:32:31 +01:00
Kconfig.debug x86: delay CPA self-test and repeat it 2008-02-06 22:39:45 +01:00
Makefile x86: define OBJCOPYFLAGS explicitly for each target. 2008-02-04 16:47:56 +01:00
Makefile_32.cpu x86: move i386 and x86_64 Makefiles to arch/x86 2007-10-25 22:27:34 +02:00