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author | Linus Torvalds <torvalds@linux-foundation.org> | 2010-01-12 18:16:42 -0800 |
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committer | H. Peter Anvin <hpa@zytor.com> | 2010-01-13 22:39:50 -0800 |
commit | bafaecd11df15ad5b1e598adc7736afcd38ee13d (patch) | |
tree | 99b676d1ecc202358fe67acd095aa2c1f1ef2b1f /arch/x86/lib | |
parent | 5d0b7235d83eefdafda300656e97d368afcafc9a (diff) | |
download | linux-3.10-bafaecd11df15ad5b1e598adc7736afcd38ee13d.tar.gz linux-3.10-bafaecd11df15ad5b1e598adc7736afcd38ee13d.tar.bz2 linux-3.10-bafaecd11df15ad5b1e598adc7736afcd38ee13d.zip |
x86-64: support native xadd rwsem implementation
This one is much faster than the spinlock based fallback rwsem code,
with certain artifical benchmarks having shown 300%+ improvement on
threaded page faults etc.
Again, note the 32767-thread limit here. So this really does need that
whole "make rwsem_count_t be 64-bit and fix the BIAS values to match"
extension on top of it, but that is conceptually a totally independent
issue.
NOT TESTED! The original patch that this all was based on were tested by
KAMEZAWA Hiroyuki, but maybe I screwed up something when I created the
cleaned-up series, so caveat emptor..
Also note that it _may_ be a good idea to mark some more registers
clobbered on x86-64 in the inline asms instead of saving/restoring them.
They are inline functions, but they are only used in places where there
are not a lot of live registers _anyway_, so doing for example the
clobbers of %r8-%r11 in the asm wouldn't make the fast-path code any
worse, and would make the slow-path code smaller.
(Not that the slow-path really matters to that degree. Saving a few
unnecessary registers is the _least_ of our problems when we hit the slow
path. The instruction/cycle counting really only matters in the fast
path).
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <alpine.LFD.2.00.1001121810410.17145@localhost.localdomain>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/lib')
-rw-r--r-- | arch/x86/lib/Makefile | 1 | ||||
-rw-r--r-- | arch/x86/lib/rwsem_64.S | 81 |
2 files changed, 82 insertions, 0 deletions
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile index cffd754f303..c80245131fd 100644 --- a/arch/x86/lib/Makefile +++ b/arch/x86/lib/Makefile @@ -39,4 +39,5 @@ else lib-y += thunk_64.o clear_page_64.o copy_page_64.o lib-y += memmove_64.o memset_64.o lib-y += copy_user_64.o rwlock_64.o copy_user_nocache_64.o + lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem_64.o endif diff --git a/arch/x86/lib/rwsem_64.S b/arch/x86/lib/rwsem_64.S new file mode 100644 index 00000000000..15acecf0d7a --- /dev/null +++ b/arch/x86/lib/rwsem_64.S @@ -0,0 +1,81 @@ +/* + * x86-64 rwsem wrappers + * + * This interfaces the inline asm code to the slow-path + * C routines. We need to save the call-clobbered regs + * that the asm does not mark as clobbered, and move the + * argument from %rax to %rdi. + * + * NOTE! We don't need to save %rax, because the functions + * will always return the semaphore pointer in %rax (which + * is also the input argument to these helpers) + * + * The following can clobber %rdx because the asm clobbers it: + * call_rwsem_down_write_failed + * call_rwsem_wake + * but %rdi, %rsi, %rcx, %r8-r11 always need saving. + */ + +#include <linux/linkage.h> +#include <asm/rwlock.h> +#include <asm/alternative-asm.h> +#include <asm/frame.h> +#include <asm/dwarf2.h> + +#define save_common_regs \ + pushq %rdi; \ + pushq %rsi; \ + pushq %rcx; \ + pushq %r8; \ + pushq %r9; \ + pushq %r10; \ + pushq %r11 + +#define restore_common_regs \ + popq %r11; \ + popq %r10; \ + popq %r9; \ + popq %r8; \ + popq %rcx; \ + popq %rsi; \ + popq %rdi + +/* Fix up special calling conventions */ +ENTRY(call_rwsem_down_read_failed) + save_common_regs + pushq %rdx + movq %rax,%rdi + call rwsem_down_read_failed + popq %rdx + restore_common_regs + ret + ENDPROC(call_rwsem_down_read_failed) + +ENTRY(call_rwsem_down_write_failed) + save_common_regs + movq %rax,%rdi + call rwsem_down_write_failed + restore_common_regs + ret + ENDPROC(call_rwsem_down_write_failed) + +ENTRY(call_rwsem_wake) + decw %dx /* do nothing if still outstanding active readers */ + jnz 1f + save_common_regs + movq %rax,%rdi + call rwsem_wake + restore_common_regs +1: ret + ENDPROC(call_rwsem_wake) + +/* Fix up special calling conventions */ +ENTRY(call_rwsem_downgrade_wake) + save_common_regs + pushq %rdx + movq %rax,%rdi + call rwsem_downgrade_wake + popq %rdx + restore_common_regs + ret + ENDPROC(call_rwsem_downgrade_wake) |