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SubjectRe: [PATCH v2 -tip] perf: x86, add SandyBridge support
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On Tue, 2011-03-01 at 15:43 +0800, Stephane Eranian wrote:
> On Mon, Feb 28, 2011 at 10:15 AM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> > On Mon, 2011-02-28 at 15:22 +0800, Lin Ming wrote:
> >> This patch adds basic SandyBridge support, including hardware cache
> >> events and PEBS events support.
> >>
> >> LLC-* hareware cache events don't work for now, it depends on the
> >> offcore patches.
> >
> > What's the status of those, Stephane reported some problems last I
> > remember?
> >
> I tried the trick I mentioned and it seems to work.

Let me make sure I understand the problem correctly.

perf top -C 0 -e LLC-loads -e LLC-store-misses

LLC-loads and LLC-store-misses events use different extra_config.

1. LLC-loads submitted successfully, era->ref=1
2. LLC-loads event is resubmitted because incremental scheduling,
era->ref=2.
3. LLC-store-misses is submitted, but fail because conflict.

Step 2 is wrong, the reference count should not be incremented with the
same event.

Is my understanding right?

Lin Ming

>
> Something like below with hwc->extra_alloc.
> Could probably find a better name for that field.
>
> 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;
>
> if (hwc->extra_alloc)
> 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;
> hwc->extra_alloc = 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;
> hwc->extra_alloc = 1;
> c = NULL;
> }
> raw_spin_unlock(&pc->lock);
> return c;
> }
>
> return NULL;
> }
>
> 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--;
> hwc->extra_alloc = 0;
> 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;
> }
> }
>
> >
> >> #define INTEL_EVENT_CONSTRAINT(c, n) \
> >> EVENT_CONSTRAINT(c, n, ARCH_PERFMON_EVENTSEL_EVENT)
> >> +#define INTEL_EVENT_CONSTRAINT2(c, n) \
> >> + EVENT_CONSTRAINT(c, n, INTEL_ARCH_EVENT_MASK)
> >
> > That's a particularly bad name, how about something like
> >
> > INTEL_UEVENT_CONSTRAINT or somesuch.
> >
> >> @@ -702,7 +738,13 @@ static void intel_ds_init(void)
> >> printk(KERN_CONT "PEBS fmt1%c, ", pebs_type);
> >> x86_pmu.pebs_record_size = sizeof(struct pebs_record_nhm);
> >> x86_pmu.drain_pebs = intel_pmu_drain_pebs_nhm;
> >> - x86_pmu.pebs_constraints = intel_nehalem_pebs_events;
> >> + switch (boot_cpu_data.x86_model) {
> >> + case 42: /* SandyBridge */
> >> + x86_pmu.pebs_constraints = intel_snb_pebs_events;
> >> + break;
> >> + default:
> >> + x86_pmu.pebs_constraints = intel_nehalem_pebs_events;
> >> + }
> >> break;
> >>
> >> default:
> >
> > We already have this massive model switch right after this function,
> > might as well move the pebs constraint assignment there.
> >




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