Messages in this thread | | | Date | Fri, 17 Oct 2008 13:13:15 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] x86: Add clflush before monitor for Intel 7400 series |
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Pallipadi, Venkatesh wrote: > > hpa, > > Do you still have reservations about this being expensive. > Note that this is only done when a CPU is about to go idle and > The cost of clflush itself will be minimal compared to idle > entry + idle exit latency. >
I guess I'm a bit confused about the tradeoff of CLFLUSH versus simply disabling MWAIT. This is a relatively recent processor and so optimizing matters (if this was a P4 I would be more worried about what has least impact on the kernel as a whole.)
Entry and exit latency do matter (specifically, exit latency matters for longer waits and the combined entry+exit latency matters for short waits.)
On the other hand, perhaps what we need to do is to get the fix in and worry about performance later.
-hpa
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