Re: [PATCH 16/28] x86/intel_rdt: Prepare to add RDT monitor cpus file support

[Shivappa Vikas]

On Tue, 1 Aug 2017, Thomas Gleixner wrote:

> On Tue, 25 Jul 2017, Vikas Shivappa wrote:
> >  /*
> >   * The cached intel_pqr_state is strictly per CPU and can never be
> >   * updated from a remote CPU. Functions which modify the state
> > @@ -49,6 +47,8 @@
> >   */
> >  DEFINE_PER_CPU(struct intel_pqr_state, pqr_state);
> >
> > +DEFINE_PER_CPU_READ_MOSTLY(struct intel_pqr_state, rdt_cpu_default);
>
> Cacheline wise this is suboptimal. You have to touch two cachelines on each
> context switch (at least for read).
>
> If you make that:
>
> struct intel_pqr_state {
> 	u32		default_cosid;
> 	u32		default_rmid;
> 	u32		cur_cosid;
> 	u32		cur_rmid;
> };
>
> DEFINE_PER_CPU(struct intel_pqr_state, pqr_state);
>
> then it's all together and you spare one cache line.

Will fix..

Thanks,
Vikas

> Thanks,
>
> 	tglx