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Date: Wed, 23 Feb 2011 10:42:43 +0800
From: Lin Ming <ming.m.lin@...el.com>
To: Stephane Eranian <eranian@...gle.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/6] perf-events: Add support for supplementary event
registers v5
On Wed, 2011-02-23 at 09:12 +0800, Stephane Eranian wrote:
> Lin,
>
> So I tested this patch on my NHM system and it has a major event scheduling
> issue. It does not ensure mutual exclusion with two offcore response events
> have different extra_config values. This is demonstrated with libpfm4:
>
> $ task -e offcore_response_0:DMND_DATA_RD:LOCAL_DRAM -e
> offcore_response_0:DMND_RFO:LOCAL_DRAM noploop 1
Hi, Stephane
$ cd libpfm4/perf_examples
$ ./task -e offcore_response_0:DMND_DATA_RD:LOCAL_DRAM -e offcore_response_0:DMND_RFO:LOCAL_DRAM ./noploop 1
noploop for 1 seconds
0 offcore_response_0:DMND_DATA_RD:LOCAL_DRAM (0.00% scaling, ena=1,000,019,277, run=1,000,019,277)
0 offcore_response_0:DMND_RFO:LOCAL_DRAM (0.00% scaling, ena=1,000,019,277, run=1,000,019,277)
The "task" example does not run well on my NHM system.
Do I miss some other setting?
Lin Ming
> PERF[type=4 val=0x5001b7 e_u=0 e_k=0 e_hv=1 period=0 freq=0 precise=0
> event_xtra=4001] offcore_response_0:DMND_DATA_RD:LOCAL_DRAM
> PERF[type=4 val=0x5001b7 e_u=0 e_k=0 e_hv=1 period=0 freq=0 precise=0
> event_xtra=4003] offcore_response_0:DMND_RFO:LOCAL_DRAM
> noploop for 1 seconds
> 283,537 offcore_response_0:DMND_DATA_RD:LOCAL_DRAM
> (99.99% scaling, ena=995,676,390, run=119,395)
> 763,110 offcore_response_0:DMND_RFO:LOCAL_DRAM (99.90%
> scaling, ena=996,675,054, run=991,306)
>
> Scaling should be 50% for 1st event, and 50% for the second. Both events are
> in separate event groups here.
>
> I tracked this down to a mismatch between intel_percore_constraints()
> and the generic layer incremental scheduling approach.
>
> The reason exclusion is not enforced is that in this case the era->ref = 2
> when it should not. The reason is pretty tricky.
>
> The scheduling algorithm schedules event groups. I illustrate this without
> the offcore response event, but just regular events:
>
> $ task -e llc_misses -e uops_retired date noploop 1
>
> // first group
> [ 397.477498] CPU0 commit_txn
> [ 397.477600] CPU0 get cpuc=ffff88007fc0b600 used=0
> per=ffff88007f80f780 cfg=13412e xtra=0
> [ 397.477672] CPU0 commit_txn ret=0
>
> // first group + second group
> [ 397.477703] CPU0 commit_txn
> [ 397.477804] CPU0 get cpuc=ffff88007fc0b600 used=0
> per=ffff88007f80f780 cfg=13412e xtra=0
> [ 397.477877] CPU0 get cpuc=ffff88007fc0b600 used=0
> per=ffff88007f80f780 cfg=1301c2 xtra=0
> [ 397.477949] CPU0 commit_txn ret=0
>
> Two groups = two calls to group_sched_in() = 2 calls to commit_txn() =
> 2 calls to x86_schedule_events()
> = 2 calls to intel_percore_constraints().
>
> In the second call, the first event is resubmitted because this is
> incremental. The scheduler needs to revisit
> the entire assignment. Thus, you have an imbalance of
> get_constraints() vs. put_constraints() in the end
> and it's game over.
>
> One may wonder how come AMD NB events don't suffer from the same
> problem, after all there is some shared
> state. I think the reason is that we track down the owner, i.e., the
> event which allocated the resource first. If we
> come twice with the same event, we don't do the allocation again.
>
> I think the problem here is slightly different, though, because you
> want to allow other events with the identical
> extra_config value. Given this is shared between HT threads, you don't
> want to release the resource and reallocate
> again because you may lose access. Maybe a solution would be to tag
> events as percore allocated, and skip
> those the second time around. There cannot be a ref++ on an event that
> has already done ref++ once and without
> callin put_constraint() in between.
>
> Anyway, there is a scheduling problem and it needs some more thinking.....
>
>
>
> On Sun, Feb 20, 2011 at 5:56 PM, Lin Ming <ming.m.lin@...el.com> wrote:
> > From: Andi Kleen <ak@...ux.intel.com>
> >
> > Intel Nehalem/Westmere have a special OFFCORE_RESPONSE event
> > that can be used to monitor any offcore accesses from a core.
> > This is a very useful event for various tunings, and it's
> > also needed to implement the generic LLC-* events correctly.
> >
> > Unfortunately this event requires programming a mask in a separate
> > register. And worse this separate register is per core, not per
> > CPU thread.
> >
> > This patch adds:
> > - Teaches perf_events that OFFCORE_RESPONSE needs extra parameters.
> > The extra parameters are passed by user space in the
> > perf_event_attr::event_extra field.
> > - Add support to the Intel perf_event core to schedule per
> > core resources. This adds fairly generic infrastructure that
> > can be also used for other per core resources.
> > The basic code has is patterned after the similar AMD northbridge
> > constraints code.
> >
> > Thanks to Stephane Eranian who pointed out some problems
> > in the original version and suggested improvements.
> >
> > Cc: eranian@...gle.com
> > Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> > Signed-off-by: Lin Ming <ming.m.lin@...el.com>
> > ---
> > arch/x86/kernel/cpu/perf_event.c | 64 ++++++++++
> > arch/x86/kernel/cpu/perf_event_intel.c | 198 ++++++++++++++++++++++++++++++++
> > include/linux/perf_event.h | 7 +-
> > 3 files changed, 268 insertions(+), 1 deletions(-)
> >
> > diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
> > index 10bfe24..de8e0bd 100644
> > --- a/arch/x86/kernel/cpu/perf_event.c
> > +++ b/arch/x86/kernel/cpu/perf_event.c
> > @@ -93,6 +93,8 @@ struct amd_nb {
> > struct event_constraint event_constraints[X86_PMC_IDX_MAX];
> > };
> >
> > +struct intel_percore;
> > +
> > #define MAX_LBR_ENTRIES 16
> >
> > struct cpu_hw_events {
> > @@ -128,6 +130,13 @@ struct cpu_hw_events {
> > struct perf_branch_entry lbr_entries[MAX_LBR_ENTRIES];
> >
> > /*
> > + * Intel percore register state.
> > + * Coordinate shared resources between HT threads.
> > + */
> > + int percore_used; /* Used by this CPU? */
> > + struct intel_percore *per_core;
> > +
> > + /*
> > * AMD specific bits
> > */
> > struct amd_nb *amd_nb;
> > @@ -175,6 +184,28 @@ struct cpu_hw_events {
> > #define for_each_event_constraint(e, c) \
> > for ((e) = (c); (e)->weight; (e)++)
> >
> > +/*
> > + * Extra registers for specific events.
> > + * Some events need large masks and require external MSRs.
> > + * Define a mapping to these extra registers.
> > + */
> > +struct extra_reg {
> > + unsigned int event;
> > + unsigned int msr;
> > + u64 config_mask;
> > + u64 valid_mask;
> > +};
> > +
> > +#define EVENT_EXTRA_REG(e, ms, m, vm) { \
> > + .event = (e), \
> > + .msr = (ms), \
> > + .config_mask = (m), \
> > + .valid_mask = (vm), \
> > + }
> > +#define INTEL_EVENT_EXTRA_REG(event, msr, vm) \
> > + EVENT_EXTRA_REG(event, msr, ARCH_PERFMON_EVENTSEL_EVENT, vm)
> > +#define EVENT_EXTRA_END EVENT_EXTRA_REG(0, 0, 0, 0)
> > +
> > union perf_capabilities {
> > struct {
> > u64 lbr_format : 6;
> > @@ -219,6 +250,7 @@ struct x86_pmu {
> > void (*put_event_constraints)(struct cpu_hw_events *cpuc,
> > struct perf_event *event);
> > struct event_constraint *event_constraints;
> > + struct event_constraint *percore_constraints;
> > void (*quirks)(void);
> > int perfctr_second_write;
> >
> > @@ -247,6 +279,11 @@ struct x86_pmu {
> > */
> > unsigned long lbr_tos, lbr_from, lbr_to; /* MSR base regs */
> > int lbr_nr; /* hardware stack size */
> > +
> > + /*
> > + * Extra registers for events
> > + */
> > + struct extra_reg *extra_regs;
> > };
> >
> > static struct x86_pmu x86_pmu __read_mostly;
> > @@ -339,6 +376,31 @@ static inline unsigned int x86_pmu_event_addr(int index)
> > return x86_pmu.perfctr + x86_pmu_addr_offset(index);
> > }
> >
> > +/*
> > + * Find and validate any extra registers to set up.
> > + */
> > +static int x86_pmu_extra_regs(u64 config, struct perf_event *event)
> > +{
> > + struct extra_reg *er;
> > +
> > + event->hw.extra_reg = 0;
> > + event->hw.extra_config = 0;
> > +
> > + if (!x86_pmu.extra_regs)
> > + return 0;
> > +
> > + for (er = x86_pmu.extra_regs; er->msr; er++) {
> > + if (er->event != (config & er->config_mask))
> > + continue;
> > + if (event->attr.event_extra & ~er->valid_mask)
> > + return -EINVAL;
> > + event->hw.extra_reg = er->msr;
> > + event->hw.extra_config = event->attr.event_extra;
> > + break;
> > + }
> > + return 0;
> > +}
> > +
> > static atomic_t active_events;
> > static DEFINE_MUTEX(pmc_reserve_mutex);
> >
> > @@ -663,6 +725,8 @@ static void x86_pmu_disable(struct pmu *pmu)
> > static inline void __x86_pmu_enable_event(struct hw_perf_event *hwc,
> > u64 enable_mask)
> > {
> > + if (hwc->extra_reg)
> > + wrmsrl(hwc->extra_reg, hwc->extra_config);
> > wrmsrl(hwc->config_base, hwc->config | enable_mask);
> > }
> >
> > diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
> > index 084b383..cc49201 100644
> > --- a/arch/x86/kernel/cpu/perf_event_intel.c
> > +++ b/arch/x86/kernel/cpu/perf_event_intel.c
> > @@ -1,5 +1,27 @@
> > #ifdef CONFIG_CPU_SUP_INTEL
> >
> > +#define MAX_EXTRA_REGS 2
> > +
> > +/*
> > + * Per register state.
> > + */
> > +struct er_account {
> > + int ref; /* reference count */
> > + unsigned int extra_reg; /* extra MSR number */
> > + u64 extra_config; /* extra MSR config */
> > +};
> > +
> > +/*
> > + * Per core state
> > + * This used to coordinate shared registers for HT threads.
> > + */
> > +struct intel_percore {
> > + raw_spinlock_t lock; /* protect structure */
> > + struct er_account regs[MAX_EXTRA_REGS];
> > + int refcnt; /* number of threads */
> > + unsigned core_id;
> > +};
> > +
> > /*
> > * Intel PerfMon, used on Core and later.
> > */
> > @@ -64,6 +86,18 @@ static struct event_constraint intel_nehalem_event_constraints[] =
> > EVENT_CONSTRAINT_END
> > };
> >
> > +static struct extra_reg intel_nehalem_extra_regs[] =
> > +{
> > + INTEL_EVENT_EXTRA_REG(0xb7, 0x1a6, 0xffff), /* OFFCORE_RESPONSE_0 */
> > + EVENT_EXTRA_END
> > +};
> > +
> > +static struct event_constraint intel_nehalem_percore_constraints[] =
> > +{
> > + INTEL_EVENT_CONSTRAINT(0xb7, 0),
> > + EVENT_CONSTRAINT_END
> > +};
> > +
> > static struct event_constraint intel_westmere_event_constraints[] =
> > {
> > FIXED_EVENT_CONSTRAINT(0x00c0, 0), /* INST_RETIRED.ANY */
> > @@ -76,6 +110,20 @@ static struct event_constraint intel_westmere_event_constraints[] =
> > EVENT_CONSTRAINT_END
> > };
> >
> > +static struct extra_reg intel_westmere_extra_regs[] =
> > +{
> > + INTEL_EVENT_EXTRA_REG(0xb7, 0x1a6, 0xffff), /* OFFCORE_RESPONSE_0 */
> > + INTEL_EVENT_EXTRA_REG(0xbb, 0x1a7, 0xffff), /* OFFCORE_RESPONSE_1 */
> > + EVENT_EXTRA_END
> > +};
> > +
> > +static struct event_constraint intel_westmere_percore_constraints[] =
> > +{
> > + INTEL_EVENT_CONSTRAINT(0xb7, 0),
> > + INTEL_EVENT_CONSTRAINT(0xbb, 0),
> > + EVENT_CONSTRAINT_END
> > +};
> > +
> > static struct event_constraint intel_gen_event_constraints[] =
> > {
> > FIXED_EVENT_CONSTRAINT(0x00c0, 0), /* INST_RETIRED.ANY */
> > @@ -794,6 +842,66 @@ intel_bts_constraints(struct perf_event *event)
> > }
> >
> > static struct event_constraint *
> > +intel_percore_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
> > +{
> > + struct hw_perf_event *hwc = &event->hw;
> > + unsigned int e = hwc->config & ARCH_PERFMON_EVENTSEL_EVENT;
> > + struct event_constraint *c;
> > + struct intel_percore *pc;
> > + struct er_account *era;
> > + int i;
> > + int free_slot;
> > + int found;
> > +
> > + if (!x86_pmu.percore_constraints)
> > + return NULL;
> > +
> > + for (c = x86_pmu.percore_constraints; c->cmask; c++) {
> > + if (e != c->code)
> > + continue;
> > +
> > + /*
> > + * Allocate resource per core.
> > + */
> > + c = NULL;
> > + pc = cpuc->per_core;
> > + if (!pc)
> > + break;
> > + c = &emptyconstraint;
> > + raw_spin_lock(&pc->lock);
> > + free_slot = -1;
> > + found = 0;
> > + for (i = 0; i < MAX_EXTRA_REGS; i++) {
> > + era = &pc->regs[i];
> > + if (era->ref > 0 && hwc->extra_reg == era->extra_reg) {
> > + /* Allow sharing same config */
> > + if (hwc->extra_config == era->extra_config) {
> > + era->ref++;
> > + cpuc->percore_used = 1;
> > + c = NULL;
> > + }
> > + /* else conflict */
> > + found = 1;
> > + break;
> > + } else if (era->ref == 0 && free_slot == -1)
> > + free_slot = i;
> > + }
> > + if (!found && free_slot != -1) {
> > + era = &pc->regs[free_slot];
> > + era->ref = 1;
> > + era->extra_reg = hwc->extra_reg;
> > + era->extra_config = hwc->extra_config;
> > + cpuc->percore_used = 1;
> > + c = NULL;
> > + }
> > + raw_spin_unlock(&pc->lock);
> > + return c;
> > + }
> > +
> > + return NULL;
> > +}
> > +
> > +static struct event_constraint *
> > intel_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
> > {
> > struct event_constraint *c;
> > @@ -806,9 +914,50 @@ intel_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event
> > if (c)
> > return c;
> >
> > + c = intel_percore_constraints(cpuc, event);
> > + if (c)
> > + return c;
> > +
> > return x86_get_event_constraints(cpuc, event);
> > }
> >
> > +static void intel_put_event_constraints(struct cpu_hw_events *cpuc,
> > + struct perf_event *event)
> > +{
> > + struct extra_reg *er;
> > + struct intel_percore *pc;
> > + struct er_account *era;
> > + struct hw_perf_event *hwc = &event->hw;
> > + int i, allref;
> > +
> > + if (!cpuc->percore_used)
> > + return;
> > +
> > + for (er = x86_pmu.extra_regs; er->msr; er++) {
> > + if (er->event != (hwc->config & er->config_mask))
> > + continue;
> > +
> > + pc = cpuc->per_core;
> > + raw_spin_lock(&pc->lock);
> > + for (i = 0; i < MAX_EXTRA_REGS; i++) {
> > + era = &pc->regs[i];
> > + if (era->ref > 0 &&
> > + era->extra_config == hwc->extra_config &&
> > + era->extra_reg == er->msr) {
> > + era->ref--;
> > + break;
> > + }
> > + }
> > + allref = 0;
> > + for (i = 0; i < MAX_EXTRA_REGS; i++)
> > + allref += pc->regs[i].ref;
> > + if (allref == 0)
> > + cpuc->percore_used = 0;
> > + raw_spin_unlock(&pc->lock);
> > + break;
> > + }
> > +}
> > +
> > static int intel_pmu_hw_config(struct perf_event *event)
> > {
> > int ret = x86_pmu_hw_config(event);
> > @@ -880,11 +1029,43 @@ static __initconst const struct x86_pmu core_pmu = {
> > */
> > .max_period = (1ULL << 31) - 1,
> > .get_event_constraints = intel_get_event_constraints,
> > + .put_event_constraints = intel_put_event_constraints,
> > .event_constraints = intel_core_event_constraints,
> > };
> >
> > +static int intel_pmu_cpu_prepare(int cpu)
> > +{
> > + struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
> > +
> > + cpuc->per_core = kzalloc_node(sizeof(struct intel_percore),
> > + GFP_KERNEL, cpu_to_node(cpu));
> > + if (!cpuc->per_core)
> > + return NOTIFY_BAD;
> > +
> > + raw_spin_lock_init(&cpuc->per_core->lock);
> > + cpuc->per_core->core_id = -1;
> > + return NOTIFY_OK;
> > +}
> > +
> > static void intel_pmu_cpu_starting(int cpu)
> > {
> > + struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
> > + int core_id = topology_core_id(cpu);
> > + int i;
> > +
> > + for_each_online_cpu(i) {
> > + struct intel_percore *pc = per_cpu(cpu_hw_events, i).per_core;
> > +
> > + if (pc && pc->core_id == core_id) {
> > + kfree(cpuc->per_core);
> > + cpuc->per_core = pc;
> > + break;
> > + }
> > + }
> > +
> > + cpuc->per_core->core_id = core_id;
> > + cpuc->per_core->refcnt++;
> > +
> > init_debug_store_on_cpu(cpu);
> > /*
> > * Deal with CPUs that don't clear their LBRs on power-up.
> > @@ -894,6 +1075,15 @@ static void intel_pmu_cpu_starting(int cpu)
> >
> > static void intel_pmu_cpu_dying(int cpu)
> > {
> > + struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
> > + struct intel_percore *pc = cpuc->per_core;
> > +
> > + if (pc) {
> > + if (pc->core_id == -1 || --pc->refcnt == 0)
> > + kfree(pc);
> > + cpuc->per_core = NULL;
> > + }
> > +
> > fini_debug_store_on_cpu(cpu);
> > }
> >
> > @@ -918,7 +1108,9 @@ static __initconst const struct x86_pmu intel_pmu = {
> > */
> > .max_period = (1ULL << 31) - 1,
> > .get_event_constraints = intel_get_event_constraints,
> > + .put_event_constraints = intel_put_event_constraints,
> >
> > + .cpu_prepare = intel_pmu_cpu_prepare,
> > .cpu_starting = intel_pmu_cpu_starting,
> > .cpu_dying = intel_pmu_cpu_dying,
> > };
> > @@ -1036,7 +1228,10 @@ static __init int intel_pmu_init(void)
> > intel_pmu_lbr_init_nhm();
> >
> > x86_pmu.event_constraints = intel_nehalem_event_constraints;
> > + x86_pmu.percore_constraints =
> > + intel_nehalem_percore_constraints;
> > x86_pmu.enable_all = intel_pmu_nhm_enable_all;
> > + x86_pmu.extra_regs = intel_nehalem_extra_regs;
> > pr_cont("Nehalem events, ");
> > break;
> >
> > @@ -1058,7 +1253,10 @@ static __init int intel_pmu_init(void)
> > intel_pmu_lbr_init_nhm();
> >
> > x86_pmu.event_constraints = intel_westmere_event_constraints;
> > + x86_pmu.percore_constraints =
> > + intel_westmere_percore_constraints;
> > x86_pmu.enable_all = intel_pmu_nhm_enable_all;
> > + x86_pmu.extra_regs = intel_westmere_extra_regs;
> > pr_cont("Westmere events, ");
> > break;
> >
> > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> > index 8ceb5a6..f531ce3 100644
> > --- a/include/linux/perf_event.h
> > +++ b/include/linux/perf_event.h
> > @@ -225,7 +225,10 @@ struct perf_event_attr {
> > };
> >
> > __u32 bp_type;
> > - __u64 bp_addr;
> > + union {
> > + __u64 bp_addr;
> > + __u64 event_extra; /* Extra for some events */
> > + };
> > __u64 bp_len;
> > };
> >
> > @@ -541,6 +544,8 @@ struct hw_perf_event {
> > unsigned long event_base;
> > int idx;
> > int last_cpu;
> > + unsigned int extra_reg;
> > + u64 extra_config;
> > };
> > struct { /* software */
> > struct hrtimer hrtimer;
> > --
> > 1.7.3
> >
> >
> >
> >
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