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| author | Andy Lutomirski <luto@MIT.EDU> | 2011-05-23 09:31:26 -0400 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2011-05-24 14:51:28 +0200 |
| commit | 3729db5ca2b2000c660e5a5d0eb68b1053212cab (patch) | |
| tree | a8b038145eadd067f92798adb4292532eccedfba /arch/x86/vdso | |
| parent | 057e6a8c660e95c3f4e7162e00e2fee1fc90c50d (diff) | |
| download | linux-3729db5ca2b2000c660e5a5d0eb68b1053212cab.tar.gz linux-3729db5ca2b2000c660e5a5d0eb68b1053212cab.tar.bz2 linux-3729db5ca2b2000c660e5a5d0eb68b1053212cab.zip | |
x86-64: Don't generate cmov in vread_tsc
vread_tsc checks whether rdtsc returns something less than
cycle_last, which is an extremely predictable branch. GCC likes
to generate a cmov anyway, which is several cycles slower than
a predicted branch. This saves a couple of nanoseconds.
Signed-off-by: Andy Lutomirski <luto@mit.edu>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Borislav Petkov <bp@amd64.org>
Link: http://lkml.kernel.org/r/%3C561280649519de41352fcb620684dfb22bad6bac.1306156808.git.luto%40mit.edu%3E
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/vdso')
0 files changed, 0 insertions, 0 deletions