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SubjectRe: [PATCH 17/21] x86/intel_rdt/cqm: Add sched_in support


On Sun, 2 Jul 2017, Thomas Gleixner wrote:

> On Mon, 26 Jun 2017, Vikas Shivappa wrote:
>> DECLARE_PER_CPU(struct intel_pqr_state, pqr_state);
>> DECLARE_PER_CPU_READ_MOSTLY(int, cpu_closid);
>> +DECLARE_PER_CPU_READ_MOSTLY(int, cpu_rmid);
>> DECLARE_STATIC_KEY_FALSE(rdt_alloc_enable_key);
>> +DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
>> +DECLARE_STATIC_KEY_FALSE(rdt_enable_key);
>
> Please make this a two stage change. Add rdt_enable_key first and then the
> monitoring stuff. Ideally you introduce rdt_enable_key here and in the
> control code in one go.
>
>> +static void __intel_rdt_sched_in(void)
>> {
>> - if (static_branch_likely(&rdt_alloc_enable_key)) {
>> - struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
>> - int closid;
>> + struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
>> + u32 closid = 0;
>> + u32 rmid = 0;
>>
>> + if (static_branch_likely(&rdt_alloc_enable_key)) {
>> /*
>> * If this task has a closid assigned, use it.
>> * Else use the closid assigned to this cpu.
>> @@ -55,14 +59,31 @@ static inline void intel_rdt_sched_in(void)
>> closid = current->closid;
>> if (closid == 0)
>> closid = this_cpu_read(cpu_closid);
>> + }
>> +
>> + if (static_branch_likely(&rdt_mon_enable_key)) {
>> + /*
>> + * If this task has a rmid assigned, use it.
>> + * Else use the rmid assigned to this cpu.
>> + */
>> + rmid = current->rmid;
>> + if (rmid == 0)
>> + rmid = this_cpu_read(cpu_rmid);
>> + }
>>
>> - if (closid != state->closid) {
>> - state->closid = closid;
>> - wrmsr(IA32_PQR_ASSOC, state->rmid, closid);
>> - }
>> + if (closid != state->closid || rmid != state->rmid) {
>> + state->closid = closid;
>> + state->rmid = rmid;
>> + wrmsr(IA32_PQR_ASSOC, rmid, closid);
>
> This can be written smarter.
>
> struct intel_pqr_state newstate = this_cpu_read(rdt_cpu_default);
> struct intel_pqr_state *curstate = this_cpu_ptr(&pqr_state);
>
> if (static_branch_likely(&rdt_alloc_enable_key)) {
> if (current->closid)
> newstate.closid = current->closid;
> }
>
> if (static_branch_likely(&rdt_mon_enable_key)) {
> if (current->rmid)
> newstate.rmid = current->rmid;
> }
>
> if (newstate != *curstate) {
> *curstate = newstate;
> wrmsr(IA32_PQR_ASSOC, newstate.rmid, newstate.closid);
> }
>
> The unconditional read of rdt_cpu_default is the right thing to do because
> the default behaviour is exactly this.

Ok makes sense. Will fix.

Thanks,
Vikas
>
> Thanks,
>
> tglx
>
>
>
>

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