Messages in this thread | | | Date | Tue, 29 Nov 2005 10:29:47 -0800 | From | John Reiser <> | Subject | Re: [Perfctr-devel] Re: Enabling RDPMC in user space by default |
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Andi Kleen wrote: > I think it's also a useful convention - RDTSC is becomming more and more > useless and you cannot expect user applications who just want to > measure some cycles to rely on ever changing instable or non existing > performance counter APIs.
Users are even more unhappy with ever-changing ABIs -- such as the kernel taking away RDTSC.
RDTSC+perfctr [Pettersson] still is the fastest way for user-mode code to count something that is highly correlated with both "billable" CPU time and "code quality" for a fixed task. With a little care RDTSC is close enough to monotonic that I find it very useful. Please don't take away user-mode RDTSC.
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