Re: [PATCH v2 -tip] perf: x86, add SandyBridge support

[Stephane Eranian]

On Mon, Feb 28, 2011 at 10:15 AM, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> 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.

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;
        }
}

>
>> Â#define INTEL_EVENT_CONSTRAINT(c, n) \
>> Â Â Â EVENT_CONSTRAINT(c, n, ARCH_PERFMON_EVENTSEL_EVENT)
>> +#define INTEL_EVENT_CONSTRAINT2(c, n) Â Â Â Â\
>> + Â Â 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)
>> Â Â Â Â Â Â Â Â Â Â Â printk(KERN_CONT "PEBS fmt1%c, ", pebs_type);
>> Â Â Â Â Â Â Â Â Â Â Â x86_pmu.pebs_record_size = sizeof(struct pebs_record_nhm);
>> Â Â Â Â Â Â Â Â Â Â Â x86_pmu.drain_pebs = intel_pmu_drain_pebs_nhm;
>> - Â Â Â Â Â Â Â Â Â Â x86_pmu.pebs_constraints = intel_nehalem_pebs_events;
>> + Â Â Â Â Â Â Â Â Â Â switch (boot_cpu_data.x86_model) {
>> + Â Â Â Â Â Â Â Â Â Â case 42: /* SandyBridge */
>> + Â Â Â Â Â Â Â Â Â Â Â Â Â Â x86_pmu.pebs_constraints = intel_snb_pebs_events;
>> + Â Â Â Â Â Â Â Â Â Â Â Â Â Â break;
>> + Â Â Â Â Â Â Â Â Â Â default:
>> + Â Â Â Â Â Â Â Â Â Â Â Â Â Â x86_pmu.pebs_constraints = intel_nehalem_pebs_events;
>> + Â Â Â Â Â Â Â Â Â Â }
>> Â Â Â Â Â Â Â Â Â Â Â break;
>>
>> Â Â Â Â Â Â Â 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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