Re: [PATCH v7 1/3] perf: cavium: Support memory controller PMU counters

From: Jonathan Cameron
Date: Mon Jul 24 2017 - 09:22:40 EST


On Mon, 24 Jul 2017 10:57:18 +0200
Jan Glauber <jan.glauber@xxxxxxxxxxxxxxxxxx> wrote:

> Hi Jonathan,
>
> On Wed, Jul 19, 2017 at 09:31:01PM +0800, Jonathan Cameron wrote:
> > On Wed, 19 Jul 2017 14:08:45 +0200
> > Jan Glauber <jglauber@xxxxxxxxxx> wrote:
> >
> > > Add support for the PMU counters on Cavium SOC memory controllers.
> > >
> > > This patch also adds generic functions to allow supporting more
> > > devices with PMU counters.
> > >
> > > Properties of the LMC PMU counters:
> > > - not stoppable
> > > - fixed purpose
> > > - read-only
> > > - one PCI device per memory controller
> > >
> > > Signed-off-by: Jan Glauber <jglauber@xxxxxxxxxx>
> > Hi Jan,
> >
> > A few little things I noticed whilst taking a quick look.
> >
> > Jonathan
> > > ---
> > > drivers/perf/Kconfig | 8 +
> > > drivers/perf/Makefile | 1 +
> > > drivers/perf/cavium_pmu.c | 416 +++++++++++++++++++++++++++++++++++++++++++++
> > > include/linux/cpuhotplug.h | 1 +
> > > 4 files changed, 426 insertions(+)
> > > create mode 100644 drivers/perf/cavium_pmu.c
> > <snip>
> > > +
> > > +/*
> > > + * The pmu events are independent from CPUs. Provide a cpumask
> > > + * nevertheless to prevent perf from adding the event per-cpu and just
> > > + * set the mask to one online CPU. Use the same cpumask for all "uncore"
> > > + * devices.
> > > + *
> > > + * There is a performance penalty for accessing a device from a CPU on
> > > + * another socket, but we do not care.
> > > + */
> > > +static int cvm_pmu_offline_cpu(unsigned int old_cpu, struct hlist_node *node)
> > > +{
> > > + struct cvm_pmu_dev *pmu_dev;
> > > + int new_cpu;
> > > +
> > > + pmu_dev = hlist_entry_safe(node, struct cvm_pmu_dev, cpuhp_node);
> > > + if (!cpumask_test_and_clear_cpu(old_cpu, &pmu_dev->active_mask))
> > > + return 0;
> > > +
> > > + new_cpu = cpumask_any_but(cpu_online_mask, old_cpu);
> > > + if (new_cpu >= nr_cpu_ids)
> > > + return 0;
> > Blank line.
>
> OK
>
> > > + perf_pmu_migrate_context(&pmu_dev->pmu, old_cpu, new_cpu);
> > > + cpumask_set_cpu(new_cpu, &pmu_dev->active_mask);
> > nitpick : blank line here would help readability.
>
> OK
>
> > > + return 0;
> > > +}
> > > +
> > > +static ssize_t cvm_pmu_attr_show_cpumask(struct device *dev,
> > > + struct device_attribute *attr,
> > > + char *buf)
> > > +{
> > > + struct pmu *pmu = dev_get_drvdata(dev);
> > > + struct cvm_pmu_dev *pmu_dev = container_of(pmu, struct cvm_pmu_dev, pmu);
> > > +
> > > + return cpumap_print_to_pagebuf(true, buf, &pmu_dev->active_mask);
> > > +}
> > > +
> > > +static DEVICE_ATTR(cpumask, S_IRUGO, cvm_pmu_attr_show_cpumask, NULL);
> > > +
> > > +static struct attribute *cvm_pmu_attrs[] = {
> > > + &dev_attr_cpumask.attr,
> > > + NULL,
> > > +};
> > > +
> > > +static struct attribute_group cvm_pmu_attr_group = {
> > > + .attrs = cvm_pmu_attrs,
> > > +};
> > > +
> > > +/*
> > > + * LMC (memory controller) counters:
> > > + * - not stoppable, always on, read-only
> > > + * - one PCI device per memory controller
> > > + */
> > > +#define LMC_CONFIG_OFFSET 0x188
> > > +#define LMC_CONFIG_RESET_BIT BIT(17)
> > > +
> > > +/* LMC events */
> > > +#define LMC_EVENT_IFB_CNT 0x1d0
> > > +#define LMC_EVENT_OPS_CNT 0x1d8
> > > +#define LMC_EVENT_DCLK_CNT 0x1e0
> > > +#define LMC_EVENT_BANK_CONFLICT1 0x360
> > > +#define LMC_EVENT_BANK_CONFLICT2 0x368
> > > +
> > > +#define CVM_PMU_LMC_EVENT_ATTR(_name, _id) \
> > > + &((struct perf_pmu_events_attr[]) { \
> > > + { \
> > > + __ATTR(_name, S_IRUGO, cvm_pmu_event_sysfs_show, NULL), \
> > > + _id, \
> > > + "lmc_event=" __stringify(_id), \
> > > + } \
> > > + })[0].attr.attr
> > > +
> > > +/* map counter numbers to register offsets */
> > > +static int lmc_events[] = {
> > > + LMC_EVENT_IFB_CNT,
> > > + LMC_EVENT_OPS_CNT,
> > > + LMC_EVENT_DCLK_CNT,
> > > + LMC_EVENT_BANK_CONFLICT1,
> > > + LMC_EVENT_BANK_CONFLICT2,
> > > +};
> > > +
> > > +static int cvm_pmu_lmc_add(struct perf_event *event, int flags)
> > > +{
> > > + struct hw_perf_event *hwc = &event->hw;
> > > +
> > > + return cvm_pmu_add(event, flags, LMC_CONFIG_OFFSET,
> > > + lmc_events[hwc->config]);
> > > +}
> > > +
> > > +PMU_FORMAT_ATTR(lmc_event, "config:0-2");
> > > +
> > > +static struct attribute *cvm_pmu_lmc_format_attr[] = {
> > > + &format_attr_lmc_event.attr,
> > > + NULL,
> > > +};
> > > +
> > > +static struct attribute_group cvm_pmu_lmc_format_group = {
> > > + .name = "format",
> > > + .attrs = cvm_pmu_lmc_format_attr,
> > > +};
> > > +
> > > +static struct attribute *cvm_pmu_lmc_events_attr[] = {
> > > + CVM_PMU_LMC_EVENT_ATTR(ifb_cnt, 0),
> > > + CVM_PMU_LMC_EVENT_ATTR(ops_cnt, 1),
> > > + CVM_PMU_LMC_EVENT_ATTR(dclk_cnt, 2),
> > > + CVM_PMU_LMC_EVENT_ATTR(bank_conflict1, 3),
> > > + CVM_PMU_LMC_EVENT_ATTR(bank_conflict2, 4),
> > > + NULL,
> > > +};
> > > +
> > > +static struct attribute_group cvm_pmu_lmc_events_group = {
> > > + .name = "events",
> > > + .attrs = cvm_pmu_lmc_events_attr,
> > > +};
> > > +
> > > +static const struct attribute_group *cvm_pmu_lmc_attr_groups[] = {
> > > + &cvm_pmu_attr_group,
> > > + &cvm_pmu_lmc_format_group,
> > > + &cvm_pmu_lmc_events_group,
> > > + NULL,
> > > +};
> > > +
> > > +static bool cvm_pmu_lmc_event_valid(u64 config)
> > > +{
> > > + return (config < ARRAY_SIZE(lmc_events));
> > > +}
> > > +
> > > +static int cvm_pmu_lmc_probe(struct pci_dev *pdev)
> > > +{
> > > + struct cvm_pmu_dev *next, *lmc;
> > > + int nr = 0, ret = -ENOMEM;
> > > +
> > > + lmc = kzalloc(sizeof(*lmc), GFP_KERNEL);
> > > + if (!lmc)
> > > + goto fail_nomem;
> > cleaner to do a direct return here as nothing to unwind.
> > return -ENOMEM;
>
> OK.
>
> > > +
> > > + lmc->map = ioremap(pci_resource_start(pdev, 0),
> > > + pci_resource_len(pdev, 0));
> > Might be overly paranoid, but ioremap can return NULL,
> > so should really be checked.
> >
>
> I'll add the check.
>
> > > + list_for_each_entry(next, &cvm_pmu_lmcs, entry)
> > > + nr++;
> > > + lmc->pmu_name = kasprintf(GFP_KERNEL, "lmc%d", nr);
> > Check for error on the allocation.
>
> OK, missed that.
>
> > > +
> > > + lmc->pdev = pdev;
> > > + lmc->num_counters = ARRAY_SIZE(lmc_events);
> > > + lmc->pmu = (struct pmu) {
> > > + .task_ctx_nr = perf_invalid_context,
> > > + .event_init = cvm_pmu_event_init,
> > > + .add = cvm_pmu_lmc_add,
> > > + .del = cvm_pmu_del,
> > > + .start = cvm_pmu_start,
> > > + .stop = cvm_pmu_stop,
> > > + .read = cvm_pmu_read,
> > > + .attr_groups = cvm_pmu_lmc_attr_groups,
> > > + };
> > > +
> > > + cpuhp_state_add_instance_nocalls(CPUHP_AP_PERF_ARM_CVM_ONLINE,
> > > + &lmc->cpuhp_node);
> > This function can fail by the look of it. Should be checking it's
> > return value really.
> >
>
> I'm ignoring the return value on purpose as I don't want probe() to fail
> even if this would return an error.
A comment perhaps to explain this.
>
> > > +
> > > + /*
> > > + * perf PMU is CPU dependent so pick a random CPU and migrate away
> > > + * if it goes offline.
> > > + */
> > > + cpumask_set_cpu(smp_processor_id(), &lmc->active_mask);
> > > +
> > > + ret = perf_pmu_register(&lmc->pmu, lmc->pmu_name, -1);
> > > + if (ret)
> > > + goto fail_hp;
> > > +
> > > + list_add(&lmc->entry, &cvm_pmu_lmcs);
> > > +
> > > + lmc->event_valid = cvm_pmu_lmc_event_valid;
> > These last two elements rather look like they might cause a
> > potential race as the perf_pmu_register has made the counters
> > available.
>
> Yes, they should happen before perf_pmu_register.
>
> > > + dev_info(&pdev->dev, "Enabled %s PMU with %d counters\n",
> > > + lmc->pmu_name, lmc->num_counters);
> > > + return 0;
> > > +
> > > +fail_hp:
> > > + kfree(lmc->pmu_name);
> > Convention is to unwind in the opposite order to the way things
> > were created / set up. Becomes more relevant once you are
> > checking more error codes.
>
> Agreed.
>
> > > + cpuhp_state_remove_instance(CPUHP_AP_PERF_ARM_CVM_ONLINE,
> > > + &lmc->cpuhp_node);
> > > + iounmap(lmc->map);
> > > + kfree(lmc);
> > > +fail_nomem:
> > > + return ret;
> > > +}
> > > +
> > > +static int __init cvm_pmu_init(void)
> > > +{
> > > + unsigned long implementor = read_cpuid_implementor();
> > > + unsigned int vendor_id = PCI_VENDOR_ID_CAVIUM;
> > > + struct pci_dev *pdev = NULL;
> > > + int rc;
> > > +
> > > + if (implementor != ARM_CPU_IMP_CAVIUM)
> > > + return -ENODEV;
> > > +
> > > + INIT_LIST_HEAD(&cvm_pmu_lmcs);
> > > +
> > > + rc = cpuhp_setup_state_multi(CPUHP_AP_PERF_ARM_CVM_ONLINE,
> > > + "perf/arm/cvm:online", NULL,
> > > + cvm_pmu_offline_cpu);
> > > +
> > > + /* detect LMC devices */
> > > + while ((pdev = pci_get_device(vendor_id, 0xa022, pdev))) {
> > > + if (!pdev)
> > > + break;
> > > + rc = cvm_pmu_lmc_probe(pdev);
> > > + if (rc)
> > > + return rc;
> > > + }
> > > + return 0;
> > > +}
> > A comment perhaps explaining why this is a late_initcall? What
> > dependency are we forcing to be true?
>
> PCI probing should be finished before, I'll add a comment.
>
> thanks for the review,
You are welcome.
> Jan
>
> > > +late_initcall(cvm_pmu_init);
> > > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> > > index b56573b..78ac3d2 100644
> > > --- a/include/linux/cpuhotplug.h
> > > +++ b/include/linux/cpuhotplug.h
> > > @@ -141,6 +141,7 @@ enum cpuhp_state {
> > > CPUHP_AP_PERF_ARM_QCOM_L3_ONLINE,
> > > CPUHP_AP_WORKQUEUE_ONLINE,
> > > CPUHP_AP_RCUTREE_ONLINE,
> > > + CPUHP_AP_PERF_ARM_CVM_ONLINE,
> > > CPUHP_AP_ONLINE_DYN,
> > > CPUHP_AP_ONLINE_DYN_END = CPUHP_AP_ONLINE_DYN + 30,
> > > CPUHP_AP_X86_HPET_ONLINE,
> >