[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86: optimize this_cpu()
On 13/07/2010 14:35, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote: > Besides the .text space savings of over 2.5k on x86-64 (1.5k for > x86-32) this removes a load (plus a lea on x86-64) from various > frequently executed code paths, and finally provides a reason (other > than legibility) to prefer this_cpu() over per_cpu() in all places > where smp_processor_id() isn't being called anyway. > > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx> > > --- 2010-06-15.orig/xen/include/asm-x86/current.h 2010-07-13 > 14:38:21.000000000 +0200 > +++ 2010-06-15/xen/include/asm-x86/current.h 2010-07-13 15:12:37.000000000 > +0200 > @@ -17,6 +17,10 @@ struct vcpu; > struct cpu_info { > struct cpu_user_regs guest_cpu_user_regs; > unsigned int processor_id; > + unsigned long per_cpu_offset; > +#ifdef __x86_64__ > + unsigned long __pad_for_stack_bottom; > +#endif That's just nasty. If we need the structure to be 16-byte aligned then we should achieve it via __attribute__((__aligned__(16))). And if we add that we may as well not ifdef it, I'm sure the up to 12 bytes padding on i386 won't cause stack overflow. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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