Messages in this thread Patch in this message | | | Date | Fri, 3 Jul 2009 12:42:34 GMT | From | tip-bot for Eric Dumazet <> | Subject | [tip:perfcounters/urgent] x86: atomic64: The atomic64_t data type should be 8 bytes aligned on 32-bit too |
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Commit-ID: bbf2a330d92c5afccfd17592ba9ccd50f41cf748 Gitweb: http://git.kernel.org/tip/bbf2a330d92c5afccfd17592ba9ccd50f41cf748 Author: Eric Dumazet <eric.dumazet@gmail.com> AuthorDate: Fri, 3 Jul 2009 00:08:26 +0200 Committer: Ingo Molnar <mingo@elte.hu> CommitDate: Fri, 3 Jul 2009 13:26:38 +0200
x86: atomic64: The atomic64_t data type should be 8 bytes aligned on 32-bit too
Locked instructions on two cache lines at once are painful. If atomic64_t uses two cache lines, my test program is 10x slower.
The chance for that is significant: 4/32 or 12.5%.
Make sure an atomic64_t is 8 bytes aligned.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> 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> [ changed it to __aligned(8) as per Andrew's suggestion ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
--- arch/x86/include/asm/atomic_32.h | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/arch/x86/include/asm/atomic_32.h b/arch/x86/include/asm/atomic_32.h index 2503d4e..ae0fbb5 100644 --- a/arch/x86/include/asm/atomic_32.h +++ b/arch/x86/include/asm/atomic_32.h @@ -250,7 +250,7 @@ static inline int atomic_add_unless(atomic_t *v, int a, int u) /* An 64bit atomic type */ typedef struct { - unsigned long long counter; + unsigned long long __aligned(8) counter; } atomic64_t; #define ATOMIC64_INIT(val) { (val) }
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