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

[David Carrillo-Cisneros <davidcc@google.com>]

if __intel_cqm_no_event_sched_in does nothing, the PQR_ASSOC msr is
still updated if state->rmid != state->next_rmid  in __pqr_update,
even if next_rmid_mode == PQR_RMID_MODE_NOEVENT .

On Fri, Apr 29, 2016 at 2:01 PM, Vikas Shivappa
<vikas.shivappa@linux.intel.com> wrote:
>
>
> On Fri, 29 Apr 2016, David Carrillo-Cisneros wrote:
>
>> 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@linux.intel.com> 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@google.com>
>>>> Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
>>>> ---
>>>> 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) ?
>
>
> Between 4 and 5 say event1 is dead. Basically on the next context switch(#5)
> if perf sched_in wasnt called the PQR still has RMID1.
>
> When you have perf_cgroup you call the __intel_cqm_no_event.. then it sees
> if there is continuous monitoring or you set the next_rmid to 0- but all the
> code there is inside #ifdef PERF_CGROUP, so without cgroup its never reset
> to zero ?
>
>
>
>>>
>>>
>>>> +
>>>> +       /* __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
>>>>
>>>>
>>>
>>
>