Messages in this thread | | | Date | Tue, 07 Oct 2008 14:32:05 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] [1/3] Provide rdtscll() asm/msr.h for user space |
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Andi Kleen wrote: > For simple user space timing it's very useful to be able to do > #include <asm/msr.h> instead of having to cut'n'paste the necessarily > macros into all programs. This used to work with older kernels, > but broke with the paravirt support (I ended up with a bunch of > test programs that broke because of that). But it's very useful > to have rdtscll() available somewhere in user space and asm/msr.h > is a good place to have them. > > Provide simple rdtsc/rdtscl() macros for user space too in asm/msr.h. > Since they are very simple I don't think they are a burden to maintain. > > The diff looks bigger than it is because I moved a code block > and diff doesn't handle it very well.
I really don't think this belongs in the kernel. It's not even a case of "usable by accident" anymore, and hasn't worked for a while, so it's not a matter of legacy, either.
Mixing fundamentally unrelated kernel and userspace variants of the same function just makes the aggregation uglier than both.
(Also, most userspace variants I have seen have what the kernel calls "rdtscll" and calls it "rdtsc".)
I would suggest writing a <sys/tsc.h> header file and submitting to the glibc people, instead, or perhaps even better, start a libarch/libx86 tree.
-hpa
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