so once more; and then I'm going to route your emails to /dev/null, wrap text at 78 chars.
On Mon, Jul 14, 2014 at 02:28:36PM +0000, Liang, Kan wrote: > > > +++ b/arch/x86/kernel/cpu/perf_event.h > > > @@ -464,6 +464,12 @@ struct x86_pmu { > > > */ > > > struct extra_reg *extra_regs; > > > unsigned int er_flags; > > > + /* > > > + * EXTRA REG MSR can be accessed > > > + * The extra registers are completely unrelated to each other. > > > + * So it needs a flag for each extra register. > > > + */ > > > + bool extra_msr_access[EXTRA_REG_MAX]; > > > > So why not in struct extra_reg again? You didn't give a straight answer > > there. > > I think I did in the email. > You mentioned that there's still (only) 4 empty bytes at the tail of > extra_reg itself. However, the extra_reg_type may be extended in the > near future. So that may not be a reason to move to extra_reg. Well, you can always grow. Also be explicit, 'may be' is an empty statement. > Furthermore, if we move extra_msr_access to extra_reg, I guess we have > to modify all the related micros (i.e EVENT_EXTRA_REG) to initialize > the new items. That could be a big change. Nah, trivial stuff :-) > On the other side, in x86_pmu structure, there are extra_regs related > items defined under the comments "Extra registers for events". And > the bit holes are enough for current usage and future extension. > > So I guess x86_pmu should be a good place to store the availability > of the reg. It just doesn't make sense to me to have multiple arrays of the same thing.
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