Re: Userspace cycle counting for loongson?

[fxzhang <fxzhang@ict.ac.cn>]

Arnaud Patard (Rtp) 写道:
> fxzhang <fxzhang@ict.ac.cn> writes:
>
>   
> > >   
> > >       
> > > > you can use mfc0/dmfc0 to read the 'count' cp0 register.
> > > >     
> > > >         
> > > afaik these instructions can't be used in userspace.
> > >   
> > >       
> > You're right:) Although some time ago I do hacked the kernel to
> > eliminate the switch of user mode/kernel mode to enable this.
> >     
>
> hmm.. would have been better if you had emulated the mfc0
> instruction like it's done for rdhwr imho :)
>
> Arnaud
>
>
>
>   
Nop, in this way, there will be some more error due to the time spent to 
access the count, and it might possibly affect the program behavior more 
due to the cache polution.