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Date: Fri, 29 Apr 2016 14:01:31 -0700 (PDT)
From: Vikas Shivappa <vikas.shivappa@...ux.intel.com>
To: David Carrillo-Cisneros <davidcc@...gle.com>
cc: Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Ingo Molnar <mingo@...hat.com>,
Matt Fleming <matt.fleming@...el.com>,
Tony Luck <tony.luck@...el.com>,
Stephane Eranian <eranian@...gle.com>,
Paul Turner <pjt@...gle.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 26/32] perf/x86/intel/cqm: integrate CQM cgroups with
scheduler
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@...ux.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@...gle.com>
>>> Signed-off-by: David Carrillo-Cisneros <davidcc@...gle.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
>>>
>>>
>>
>
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