Messages in this thread Patch in this message | | | Date | Fri, 3 Jul 2009 12:44:18 GMT | From | tip-bot for Eric Dumazet <> | Subject | [tip:perfcounters/urgent] x86: atomic64: Improve atomic64_read() |
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Commit-ID: 9103cab145a93cef13378632b332a824758a2f6f Gitweb: http://git.kernel.org/tip/9103cab145a93cef13378632b332a824758a2f6f Author: Eric Dumazet <eric.dumazet@gmail.com> AuthorDate: Fri, 3 Jul 2009 13:23:02 +0200 Committer: Ingo Molnar <mingo@elte.hu> CommitDate: Fri, 3 Jul 2009 13:26:48 +0200
x86: atomic64: Improve atomic64_read()
Optimize atomic64_read() as a special open-coded cmpxchg8b variant. This generates nicer code:
arch/x86/lib/atomic64_32.o:
text data bss dec hex filename 435 0 0 435 1b3 atomic64_32.o.before 431 0 0 431 1af atomic64_32.o.after
md5: bd8ab95e69c93518578bfaf0ea3be4d9 atomic64_32.o.before.asm 2bdfd4bd1f6b7b61b7fc127aef90ce3b atomic64_32.o.after.asm
Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: David Howells <dhowells@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Arnd Bergmann <arnd@arndb.de> LKML-Reference: <alpine.LFD.2.01.0907021653030.3210@localhost.localdomain> Signed-off-by: Ingo Molnar <mingo@elte.hu>
--- arch/x86/lib/atomic64_32.c | 12 ++++++++++-- 1 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/arch/x86/lib/atomic64_32.c b/arch/x86/lib/atomic64_32.c index fd28fd3..079ac8e 100644 --- a/arch/x86/lib/atomic64_32.c +++ b/arch/x86/lib/atomic64_32.c @@ -62,9 +62,17 @@ void atomic64_set(atomic64_t *ptr, u64 new_val) */ u64 atomic64_read(atomic64_t *ptr) { - u64 old = 1LL << 32; + u64 res; - return cmpxchg8b(&ptr->counter, old, old); + asm volatile( + "mov %%ebx, %%eax\n\t" + "mov %%ecx, %%edx\n\t" + LOCK_PREFIX "cmpxchg8b %1\n" + : "=A" (res) + : "m" (*ptr) + ); + + return res; } /**
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