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