From bafaecd11df15ad5b1e598adc7736afcd38ee13d Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 12 Jan 2010 18:16:42 -0800 Subject: 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 LKML-Reference: Signed-off-by: H. Peter Anvin --- arch/x86/lib/Makefile | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/lib/Makefile') diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile index cffd754f3039..c80245131fdc 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 -- cgit v1.2.3