Commit 685db65e authored Mar 02, 2006 by Christoph Lameter Committed by Linus Torvalds Mar 02, 2006

[PATCH] time_interpolator: Use readq_relaxed() instead of readq().



On some platforms readq performs additional work to make sure I/O is done
in a coherent way.  This is not needed for time retrieval as done by the
time interpolator.  So we can use readq_relaxed instead which will improve
performance.

It affects sparc64 and ia64 only.  Apparently it makes a significant
difference on ia64.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: john stultz <johnstul@us.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent 7f99f06f

kernel/timer.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1351,10 +1351,10 @@ static inline u64 time_interpolator_get_cycles(unsigned int src)
		return x();

		case TIME_SOURCE_MMIO64 :
		return readq((void __iomem *) time_interpolator->addr);
		return readq_relaxed((void __iomem *)time_interpolator->addr);

		case TIME_SOURCE_MMIO32 :
		return readl((void __iomem *) time_interpolator->addr);
		return readl_relaxed((void __iomem *)time_interpolator->addr);

		default: return get_cycles();
		}

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