Re: [PATCH 26/32] perf/x86/intel/cqm: integrate CQM cgroups with scheduler

[David Carrillo-Cisneros]

Not sure I see the problem you point here. In step 3, PQR_ASSOC is
updated with RMID1, __pqr_update is the one called using the scheduler
hook, right after perf sched_in .

On Fri, Apr 29, 2016 at 1:25 PM, Vikas Shivappa
<vikas.shivappa@xxxxxxxxxxxxxxx> wrote:
>
>
> On Thu, 28 Apr 2016, David Carrillo-Cisneros wrote:
>
>> Allow monitored cgroups to update the PQR MSR during task switch even
>> without an associated perf_event.
>>
>> The package RMID for the current monr associated with a monitored
>> cgroup is written to hw during task switch (after perf_events is run)
>> if perf_event did not write a RMID for an event.
>>
>> perf_event and any other caller of pqr_cache_update_rmid can update the
>> CPU's RMID using one of two modes:
>>  - PQR_RMID_MODE_NOEVENT: A RMID that do not correspond to an event.
>>    e.g. the RMID of the root pmonr when no event is scheduled.
>>  - PQR_RMID_MODE_EVENT:   A RMID used by an event. Set during pmu::add
>> unset on pmu::del. This mode prevents from using a non-event
>> cgroup RMID.
>>
>> This patch also introduces caching of writes to PQR MSR within the per-pcu
>> pqr state variable. This interface to update RMIDs and CLOSIDs will be
>> also utilized in upcoming versions of Intel's MBM and CAT drivers.
>>
>> Reviewed-by: Stephane Eranian <eranian@xxxxxxxxxx>
>> Signed-off-by: David Carrillo-Cisneros <davidcc@xxxxxxxxxx>
>> ---
>> arch/x86/events/intel/cqm.c       | 65
>> +++++++++++++++++++++++++++++----------
>> arch/x86/events/intel/cqm.h       |  2 --
>> arch/x86/include/asm/pqr_common.h | 53 +++++++++++++++++++++++++++----
>> arch/x86/kernel/cpu/pqr_common.c  | 46 +++++++++++++++++++++++----
>> 4 files changed, 135 insertions(+), 31 deletions(-)
>>
>> diff --git a/arch/x86/events/intel/cqm.c b/arch/x86/events/intel/cqm.c
>> index daf9fdf..4ece0a4 100644
>> --- a/arch/x86/events/intel/cqm.c
>> +++ b/arch/x86/events/intel/cqm.c
>> @@ -198,19 +198,6 @@ static inline int cqm_prmid_update(struct prmid
>> *prmid)
>>         return __cqm_prmid_update(prmid, __rmid_min_update_time);
>> }
>>
>> -/*
>> - * Updates caller cpu's cache.
>> - */
>> -static inline void __update_pqr_prmid(struct prmid *prmid)
>> -{
>> -       struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
>> -
>> -       if (state->rmid == prmid->rmid)
>> -               return;
>> -       state->rmid = prmid->rmid;
>> -       wrmsr(MSR_IA32_PQR_ASSOC, prmid->rmid, state->closid);
>> -}
>> -
>> static inline bool __valid_pkg_id(u16 pkg_id)
>> {
>>         return pkg_id < PQR_MAX_NR_PKGS;
>> @@ -2531,12 +2518,11 @@ static inline bool cqm_group_leader(struct
>> perf_event *event)
>> static inline void __intel_cqm_event_start(
>>         struct perf_event *event, union prmid_summary summary)
>> {
>> -       u16 pkg_id = topology_physical_package_id(smp_processor_id());
>>         if (!(event->hw.state & PERF_HES_STOPPED))
>>                 return;
>> -
>>         event->hw.state &= ~PERF_HES_STOPPED;
>> -       __update_pqr_prmid(__prmid_from_rmid(pkg_id, summary.sched_rmid));
>> +
>> +       pqr_cache_update_rmid(summary.sched_rmid, PQR_RMID_MODE_EVENT);
>> }
>>
>> static void intel_cqm_event_start(struct perf_event *event, int mode)
>> @@ -2566,7 +2552,7 @@ static void intel_cqm_event_stop(struct perf_event
>> *event, int mode)
>>         /* Occupancy of CQM events is obtained at read. No need to read
>>          * when event is stopped since read on inactive cpus succeed.
>>          */
>> -       __update_pqr_prmid(__prmid_from_rmid(pkg_id, summary.sched_rmid));
>> +       pqr_cache_update_rmid(summary.sched_rmid, PQR_RMID_MODE_NOEVENT);
>> }
>>
>> static int intel_cqm_event_add(struct perf_event *event, int mode)
>> @@ -2977,6 +2963,8 @@ static void intel_cqm_cpu_starting(unsigned int cpu)
>>
>>         state->rmid = 0;
>>         state->closid = 0;
>> +       state->next_rmid = 0;
>> +       state->next_closid = 0;
>>
>>         /* XXX: lock */
>>         /* XXX: Make sure this case is handled when hotplug happens. */
>> @@ -3152,6 +3140,12 @@ static int __init intel_cqm_init(void)
>>         pr_info("Intel CQM monitoring enabled with at least %u rmids per
>> package.\n",
>>                 min_max_rmid + 1);
>>
>> +       /* Make sure pqr_common_enable_key is enabled after
>> +        * cqm_initialized_key.
>> +        */
>> +       barrier();
>> +
>> +       static_branch_enable(&pqr_common_enable_key);
>>         return ret;
>>
>> error_init_mutex:
>> @@ -3163,4 +3157,41 @@ error:
>>         return ret;
>> }
>>
>> +/* Schedule task without a CQM perf_event. */
>> +inline void __intel_cqm_no_event_sched_in(void)
>> +{
>> +#ifdef CONFIG_CGROUP_PERF
>> +       struct monr *monr;
>> +       struct pmonr *pmonr;
>> +       union prmid_summary summary;
>> +       u16 pkg_id = topology_physical_package_id(smp_processor_id());
>> +       struct pmonr *root_pmonr = monr_hrchy_root->pmonrs[pkg_id];
>> +
>> +       /* Assume CQM enabled is likely given that PQR is enabled. */
>> +       if (!static_branch_likely(&cqm_initialized_key))
>> +               return;
>> +
>> +       /* Safe to call from_task since we are in scheduler lock. */
>> +       monr = monr_from_perf_cgroup(perf_cgroup_from_task(current,
>> NULL));
>> +       pmonr = monr->pmonrs[pkg_id];
>> +
>> +       /* Utilize most up to date pmonr summary. */
>> +       monr_hrchy_get_next_prmid_summary(pmonr);
>> +       summary.value = atomic64_read(&pmonr->prmid_summary_atomic);
>> +
>> +       if (!prmid_summary__is_mon_active(summary))
>> +               goto no_rmid;
>> +
>> +       if (WARN_ON_ONCE(!__valid_rmid(pkg_id, summary.sched_rmid)))
>> +               goto no_rmid;
>> +
>> +       pqr_cache_update_rmid(summary.sched_rmid, PQR_RMID_MODE_NOEVENT);
>> +       return;
>> +
>> +no_rmid:
>> +       summary.value = atomic64_read(&root_pmonr->prmid_summary_atomic);
>> +       pqr_cache_update_rmid(summary.sched_rmid, PQR_RMID_MODE_NOEVENT);
>> +#endif
>> +}
>> +
>> device_initcall(intel_cqm_init);
>> diff --git a/arch/x86/events/intel/cqm.h b/arch/x86/events/intel/cqm.h
>> index 0f3da94..e1f8bd0 100644
>> --- a/arch/x86/events/intel/cqm.h
>> +++ b/arch/x86/events/intel/cqm.h
>> @@ -82,8 +82,6 @@ union prmid_summary {
>>         };
>> };
>>
>> -# define INVALID_RMID (-1)
>> -
>> /* A pmonr in (U)state has no sched_rmid, read_rmid can be 0 or
>> INVALID_RMID
>>  * depending on whether monitoring is active or not.
>>  */
>> diff --git a/arch/x86/include/asm/pqr_common.h
>> b/arch/x86/include/asm/pqr_common.h
>> index f770637..abbb235 100644
>> --- a/arch/x86/include/asm/pqr_common.h
>> +++ b/arch/x86/include/asm/pqr_common.h
>> @@ -3,31 +3,72 @@
>>
>> #if defined(CONFIG_INTEL_RDT)
>>
>> +#include <linux/jump_label.h>
>> #include <linux/types.h>
>> #include <asm/percpu.h>
>> +#include <asm/msr.h>
>>
>> #define MSR_IA32_PQR_ASSOC      0x0c8f
>> +#define INVALID_RMID           (-1)
>> +#define INVALID_CLOSID         (-1)
>> +
>> +
>> +extern struct static_key_false pqr_common_enable_key;
>> +
>> +enum intel_pqr_rmid_mode {
>> +       /* RMID has no perf_event associated. */
>> +       PQR_RMID_MODE_NOEVENT = 0,
>> +       /* RMID has a perf_event associated. */
>> +       PQR_RMID_MODE_EVENT
>> +};
>>
>> /**
>>  * struct intel_pqr_state - State cache for the PQR MSR
>> - * @rmid:              The cached Resource Monitoring ID
>> - * @closid:            The cached Class Of Service ID
>> + * @rmid:              Last rmid written to hw.
>> + * @next_rmid:         Next rmid to write to hw.
>> + * @next_rmid_mode:    Next rmid's mode.
>> + * @closid:            The current Class Of Service ID
>> + * @next_closid:       The Class Of Service ID to use.
>>  *
>>  * The upper 32 bits of MSR_IA32_PQR_ASSOC contain closid and the
>>  * lower 10 bits rmid. The update to MSR_IA32_PQR_ASSOC always
>>  * contains both parts, so we need to cache them.
>>  *
>> - * The cache also helps to avoid pointless updates if the value does
>> - * not change.
>> + * The cache also helps to avoid pointless updates if the value does not
>> + * change. It also keeps track of the type of RMID set (event vs no
>> event)
>> + * used to determine when a cgroup RMID is required.
>>  */
>> struct intel_pqr_state {
>> -       u32                     rmid;
>> -       u32                     closid;
>> +       u32                             rmid;
>> +       u32                             next_rmid;
>> +       enum intel_pqr_rmid_mode        next_rmid_mode;
>> +       u32                             closid;
>> +       u32                             next_closid;
>> };
>>
>> DECLARE_PER_CPU(struct intel_pqr_state, pqr_state);
>>
>> #define PQR_MAX_NR_PKGS         8
>>
>> +void __pqr_update(void);
>> +
>> +inline void __intel_cqm_no_event_sched_in(void);
>> +
>> +inline void pqr_cache_update_rmid(u32 rmid, enum intel_pqr_rmid_mode
>> mode);
>> +
>> +inline void pqr_cache_update_closid(u32 closid);
>> +
>> +static inline void pqr_update(void)
>> +{
>> +       if (static_branch_unlikely(&pqr_common_enable_key))
>> +               __pqr_update();
>> +}
>> +
>> +#else
>> +
>> +static inline void pqr_update(void)
>> +{
>> +}
>> +
>> #endif
>> #endif
>> diff --git a/arch/x86/kernel/cpu/pqr_common.c
>> b/arch/x86/kernel/cpu/pqr_common.c
>> index 9eff5d9..d91c127 100644
>> --- a/arch/x86/kernel/cpu/pqr_common.c
>> +++ b/arch/x86/kernel/cpu/pqr_common.c
>> @@ -1,9 +1,43 @@
>> #include <asm/pqr_common.h>
>>
>> -/*
>> - * The cached intel_pqr_state is strictly per CPU and can never be
>> - * updated from a remote CPU. Both functions which modify the state
>> - * (intel_cqm_event_start and intel_cqm_event_stop) are called with
>> - * interrupts disabled, which is sufficient for the protection.
>> - */
>> DEFINE_PER_CPU(struct intel_pqr_state, pqr_state);
>> +
>> +DEFINE_STATIC_KEY_FALSE(pqr_common_enable_key);
>> +
>> +inline void pqr_cache_update_rmid(u32 rmid, enum intel_pqr_rmid_mode
>> mode)
>> +{
>> +       struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
>> +
>> +       state->next_rmid_mode = mode;
>> +       state->next_rmid = rmid;
>> +}
>> +
>> +inline void pqr_cache_update_closid(u32 closid)
>> +{
>> +       struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
>> +
>> +       state->next_closid = closid;
>> +}
>> +
>> +/* Update hw's RMID using cgroup's if perf_event did not.
>> + * Sync pqr cache with MSR.
>> + */
>> +inline void __pqr_update(void)
>> +{
>> +       struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
>> +
>> +       /* If perf_event has set a next_rmid that is used, do not try
>> +        * to obtain another one from current task.
>> +        */
>> +       if (state->next_rmid_mode == PQR_RMID_MODE_NOEVENT)
>> +               __intel_cqm_no_event_sched_in();
>
>
> if perf_cgroup is not defined then the state is not updated here so the
> state might have state->rmid might have IDs ?
>
> 1.event1 for PID1 has RMID1,
> 2.perf sched_in - state->next_rmid = rmid1
> 3.pqr_update - state->rmid = rmid1
> 4.sched_out - write PQR_NOEVENT -
> 5.next switch_to - state->rmid not reset nothing changes (when no
> perf_cgroup) ?
>
>
>> +
>> +       /* __intel_cqm_no_event_sched_in might have changed next_rmid. */
>> +       if (state->rmid == state->next_rmid &&
>> +           state->closid == state->next_closid)
>> +               return;
>> +
>> +       state->rmid = state->next_rmid;
>> +       state->closid = state->next_closid;
>> +       wrmsr(MSR_IA32_PQR_ASSOC, state->rmid, state->closid);
>> +}
>> --
>> 2.8.0.rc3.226.g39d4020
>>
>>
>