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authorAndi Kleen <ak@suse.de>2006-09-26 10:52:41 +0200
committerAndi Kleen <andi@basil.nowhere.org>2006-09-26 10:52:41 +0200
commit2049336f60d297c85ac977245b9326ec00396114 (patch)
treeb7af9b104177e32d100289e9cb174d71767c9ce5
parent9ddab42d1e65dfbdb14588346d47fb142090ab40 (diff)
[PATCH] Don't synchronize time reading on single core AMD systems
We do some additional CPU synchronization in gettimeofday et.al. to make sure the time stamps are always monotonic over multiple CPUs. But on single core systems that is not needed. So don't do it. Signed-off-by: Andi Kleen <ak@suse.de>
-rw-r--r--arch/x86_64/kernel/setup.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index 085f2e09b9d..26524ce3b23 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -728,6 +728,12 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
/* Fix cpuid4 emulation for more */
num_cache_leaves = 3;
+
+ /* When there is only one core no need to synchronize RDTSC */
+ if (num_possible_cpus() == 1)
+ set_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
+ else
+ clear_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
}
static void __cpuinit detect_ht(struct cpuinfo_x86 *c)