Re: [PATCH v4 1/5] arm64: perf: Basic uncore counter support for Cavium ThunderX SOC

[Will Deacon]

Hi Jan,

Thanks for posting an updated series. I have a few minor comments, which
we can hopefully address in time for 4.10.

Also, have you run the perf fuzzer with this series applied?

https://github.com/deater/perf_event_tests

(build the tests and look under the fuzzer/ directory for the tool)

On Sat, Oct 29, 2016 at 01:55:29PM +0200, Jan Glauber wrote:
> Provide "uncore" facilities for different non-CPU performance
> counter units.
> 
> The uncore PMUs can be found under /sys/bus/event_source/devices.
> All counters are exported via sysfs in the corresponding events
> files under the PMU directory so the perf tool can list the event names.
> 
> There are some points that are special in this implementation:
> 
> 1) The PMU detection relies on PCI device detection. If a
>    matching PCI device is found the PMU is created. The code can deal
>    with multiple units of the same type, e.g. more than one memory
>    controller.
> 
> 2) Counters are summarized across different units of the same type
>    on one NUMA node but not across NUMA nodes.
>    For instance L2C TAD 0..7 are presented as a single counter
>    (adding the values from TAD 0 to 7). Although losing the ability
>    to read a single value the merged values are easier to use.
> 
> 3) The counters are not CPU related. A random CPU is picked regardless
>    of the NUMA node. There is a small performance penalty for accessing
>    counters on a remote note but reading a performance counter is a
>    slow operation anyway.
> 
> Signed-off-by: Jan Glauber <jglauber@xxxxxxxxxx>
> ---
>  drivers/perf/Kconfig                |  13 ++
>  drivers/perf/Makefile               |   1 +
>  drivers/perf/uncore/Makefile        |   1 +
>  drivers/perf/uncore/uncore_cavium.c | 351 ++++++++++++++++++++++++++++++++++++
>  drivers/perf/uncore/uncore_cavium.h |  71 ++++++++

We already have "uncore" PMUs under drivers/perf, so I'd prefer that we
renamed this a bit to reflect better what's going on. How about:

  drivers/perf/cavium/

and then

  drivers/perf/cavium/uncore_thunder.[ch]

?

>  include/linux/cpuhotplug.h          |   1 +
>  6 files changed, 438 insertions(+)
>  create mode 100644 drivers/perf/uncore/Makefile
>  create mode 100644 drivers/perf/uncore/uncore_cavium.c
>  create mode 100644 drivers/perf/uncore/uncore_cavium.h
> 
> diff --git a/drivers/perf/Kconfig b/drivers/perf/Kconfig
> index 4d5c5f9..3266c87 100644
> --- a/drivers/perf/Kconfig
> +++ b/drivers/perf/Kconfig
> @@ -19,4 +19,17 @@ config XGENE_PMU
>          help
>            Say y if you want to use APM X-Gene SoC performance monitors.
>  
> +config UNCORE_PMU
> +	bool

This isn't needed.

> +
> +config UNCORE_PMU_CAVIUM
> +	depends on PERF_EVENTS && NUMA && ARM64
> +	bool "Cavium uncore PMU support"

Please mentioned Thunder somewhere, since that's the SoC being supported.

> +	select UNCORE_PMU
> +	default y
> +	help
> +	  Say y if you want to access performance counters of subsystems
> +	  on a Cavium SOC like cache controller, memory controller or
> +	  processor interconnect.
> +
>  endmenu
> diff --git a/drivers/perf/Makefile b/drivers/perf/Makefile
> index b116e98..d6c02c9 100644
> --- a/drivers/perf/Makefile
> +++ b/drivers/perf/Makefile
> @@ -1,2 +1,3 @@
>  obj-$(CONFIG_ARM_PMU) += arm_pmu.o
>  obj-$(CONFIG_XGENE_PMU) += xgene_pmu.o
> +obj-y += uncore/
> diff --git a/drivers/perf/uncore/Makefile b/drivers/perf/uncore/Makefile
> new file mode 100644
> index 0000000..6130e18
> --- /dev/null
> +++ b/drivers/perf/uncore/Makefile
> @@ -0,0 +1 @@
> +obj-$(CONFIG_UNCORE_PMU_CAVIUM) += uncore_cavium.o
> diff --git a/drivers/perf/uncore/uncore_cavium.c b/drivers/perf/uncore/uncore_cavium.c
> new file mode 100644
> index 0000000..a7b4277
> --- /dev/null
> +++ b/drivers/perf/uncore/uncore_cavium.c
> @@ -0,0 +1,351 @@
> +/*
> + * Cavium Thunder uncore PMU support.
> + *
> + * Copyright (C) 2015,2016 Cavium Inc.
> + * Author: Jan Glauber <jan.glauber@xxxxxxxxxx>
> + */
> +
> +#include <linux/cpufeature.h>
> +#include <linux/numa.h>
> +#include <linux/slab.h>
> +
> +#include "uncore_cavium.h"
> +
> +/*
> + * Some notes about the various counters supported by this "uncore" PMU
> + * and the design:
> + *
> + * All counters are 64 bit long.
> + * There are no overflow interrupts.
> + * Counters are summarized per node/socket.
> + * Most devices appear as separate PCI devices per socket with the exception
> + * of OCX TLK which appears as one PCI device per socket and contains several
> + * units with counters that are merged.
> + * Some counters are selected via a control register (L2C TAD) and read by
> + * a number of counter registers, others (L2C CBC, LMC & OCX TLK) have
> + * one dedicated counter per event.
> + * Some counters are not stoppable (L2C CBC & LMC).
> + * Some counters are read-only (LMC).
> + * All counters belong to PCI devices, the devices may have additional
> + * drivers but we assume we are the only user of the counter registers.
> + * We map the whole PCI BAR so we must be careful to forbid access to
> + * addresses that contain neither counters nor counter control registers.
> + */
> +
> +void thunder_uncore_read(struct perf_event *event)
> +{

Rather than have a bunch of global symbols that are called from the
individual drivers, why don't you pass a struct of function pointers to
their respective init functions and keep the internals private?

> +	struct thunder_uncore *uncore = to_uncore(event->pmu);
> +	struct hw_perf_event *hwc = &event->hw;
> +	struct thunder_uncore_node *node;
> +	struct thunder_uncore_unit *unit;
> +	u64 prev, delta, new = 0;
> +
> +	node = get_node(hwc->config, uncore);
> +
> +	/* read counter values from all units on the node */
> +	list_for_each_entry(unit, &node->unit_list, entry)
> +		new += readq(hwc->event_base + unit->map);
> +
> +	prev = local64_read(&hwc->prev_count);
> +	local64_set(&hwc->prev_count, new);
> +	delta = new - prev;
> +	local64_add(delta, &event->count);
> +}
> +
> +int thunder_uncore_add(struct perf_event *event, int flags, u64 config_base,
> +		       u64 event_base)
> +{
> +	struct thunder_uncore *uncore = to_uncore(event->pmu);
> +	struct hw_perf_event *hwc = &event->hw;
> +	struct thunder_uncore_node *node;
> +	int id;
> +
> +	node = get_node(hwc->config, uncore);
> +	id = get_id(hwc->config);
> +
> +	if (!cmpxchg(&node->events[id], NULL, event))
> +		hwc->idx = id;

Does this need to be a full-fat cmpxchg? Who are you racing with?

> +
> +	if (hwc->idx == -1)
> +		return -EBUSY;

This would be much clearer as an else statement after the cmpxchg.

> +
> +	hwc->config_base = config_base;
> +	hwc->event_base = event_base;
> +	hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
> +
> +	if (flags & PERF_EF_START)
> +		uncore->pmu.start(event, PERF_EF_RELOAD);
> +
> +	return 0;
> +}
> +
> +void thunder_uncore_del(struct perf_event *event, int flags)
> +{
> +	struct thunder_uncore *uncore = to_uncore(event->pmu);
> +	struct hw_perf_event *hwc = &event->hw;
> +	struct thunder_uncore_node *node;
> +	int i;
> +
> +	event->pmu->stop(event, PERF_EF_UPDATE);
> +
> +	/*
> +	 * For programmable counters we need to check where we installed it.
> +	 * To keep this function generic always test the more complicated
> +	 * case (free running counters won't need the loop).
> +	 */
> +	node = get_node(hwc->config, uncore);
> +	for (i = 0; i < node->num_counters; i++) {
> +		if (cmpxchg(&node->events[i], event, NULL) == event)
> +			break;
> +	}
> +	hwc->idx = -1;
> +}
> +
> +void thunder_uncore_start(struct perf_event *event, int flags)
> +{
> +	struct thunder_uncore *uncore = to_uncore(event->pmu);
> +	struct hw_perf_event *hwc = &event->hw;
> +	struct thunder_uncore_node *node;
> +	struct thunder_uncore_unit *unit;
> +	u64 new = 0;
> +
> +	/* read counter values from all units on the node */
> +	node = get_node(hwc->config, uncore);
> +	list_for_each_entry(unit, &node->unit_list, entry)
> +		new += readq(hwc->event_base + unit->map);
> +	local64_set(&hwc->prev_count, new);
> +
> +	hwc->state = 0;
> +	perf_event_update_userpage(event);
> +}
> +
> +void thunder_uncore_stop(struct perf_event *event, int flags)
> +{
> +	struct hw_perf_event *hwc = &event->hw;
> +
> +	hwc->state |= PERF_HES_STOPPED;
> +
> +	if ((flags & PERF_EF_UPDATE) && !(hwc->state & PERF_HES_UPTODATE)) {
> +		thunder_uncore_read(event);
> +		hwc->state |= PERF_HES_UPTODATE;
> +	}
> +}
> +
> +int thunder_uncore_event_init(struct perf_event *event)
> +{
> +	struct hw_perf_event *hwc = &event->hw;
> +	struct thunder_uncore_node *node;
> +	struct thunder_uncore *uncore;
> +
> +	if (event->attr.type != event->pmu->type)
> +		return -ENOENT;
> +
> +	/* we do not support sampling */
> +	if (is_sampling_event(event))
> +		return -EINVAL;
> +
> +	/* counters do not have these bits */
> +	if (event->attr.exclude_user	||
> +	    event->attr.exclude_kernel	||
> +	    event->attr.exclude_host	||
> +	    event->attr.exclude_guest	||
> +	    event->attr.exclude_hv	||
> +	    event->attr.exclude_idle)
> +		return -EINVAL;
> +
> +	uncore = to_uncore(event->pmu);
> +	if (!uncore)
> +		return -ENODEV;
> +	if (!uncore->event_valid(event->attr.config & UNCORE_EVENT_ID_MASK))
> +		return -EINVAL;
> +
> +	/* check NUMA node */
> +	node = get_node(event->attr.config, uncore);
> +	if (!node) {
> +		pr_debug("Invalid NUMA node selected\n");
> +		return -EINVAL;
> +	}
> +
> +	hwc->config = event->attr.config;
> +	hwc->idx = -1;
> +	return 0;
> +}
> +
> +static ssize_t thunder_uncore_attr_show_cpumask(struct device *dev,
> +						struct device_attribute *attr,
> +						char *buf)
> +{
> +	struct pmu *pmu = dev_get_drvdata(dev);
> +	struct thunder_uncore *uncore =
> +		container_of(pmu, struct thunder_uncore, pmu);
> +
> +	return cpumap_print_to_pagebuf(true, buf, &uncore->active_mask);
> +}
> +static DEVICE_ATTR(cpumask, S_IRUGO, thunder_uncore_attr_show_cpumask, NULL);
> +
> +static struct attribute *thunder_uncore_attrs[] = {
> +	&dev_attr_cpumask.attr,
> +	NULL,
> +};
> +
> +struct attribute_group thunder_uncore_attr_group = {
> +	.attrs = thunder_uncore_attrs,
> +};
> +
> +ssize_t thunder_events_sysfs_show(struct device *dev,
> +				  struct device_attribute *attr,
> +				  char *page)
> +{
> +	struct perf_pmu_events_attr *pmu_attr =
> +		container_of(attr, struct perf_pmu_events_attr, attr);
> +
> +	if (pmu_attr->event_str)
> +		return sprintf(page, "%s", pmu_attr->event_str);
> +
> +	return 0;
> +}
> +
> +/* node attribute depending on number of NUMA nodes */
> +static ssize_t node_show(struct device *dev, struct device_attribute *attr,
> +			 char *page)
> +{
> +	if (NODES_SHIFT)
> +		return sprintf(page, "config:16-%d\n", 16 + NODES_SHIFT - 1);

If NODES_SHIFT is 1, you'll end up with "config:16-16", which might confuse
userspace.

> +	else
> +		return sprintf(page, "config:16\n");
> +}
> +
> +struct device_attribute format_attr_node = __ATTR_RO(node);
> +
> +/*
> + * Thunder uncore 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 (yet).
> + */
> +static int thunder_uncore_offline_cpu(unsigned int old_cpu, struct hlist_node *node)
> +{
> +	struct thunder_uncore *uncore = hlist_entry_safe(node, struct thunder_uncore, node);

Why _safe?

> +	int new_cpu;
> +
> +	if (!cpumask_test_and_clear_cpu(old_cpu, &uncore->active_mask))
> +		return 0;
> +	new_cpu = cpumask_any_but(cpu_online_mask, old_cpu);
> +	if (new_cpu >= nr_cpu_ids)
> +		return 0;
> +	perf_pmu_migrate_context(&uncore->pmu, old_cpu, new_cpu);
> +	cpumask_set_cpu(new_cpu, &uncore->active_mask);
> +	return 0;
> +}
> +
> +static struct thunder_uncore_node * __init alloc_node(struct thunder_uncore *uncore,
> +						      int node_id, int counters)
> +{
> +	struct thunder_uncore_node *node;
> +
> +	node = kzalloc(sizeof(*node), GFP_KERNEL);
> +	if (!node)
> +		return NULL;
> +	node->num_counters = counters;
> +	INIT_LIST_HEAD(&node->unit_list);
> +	return node;
> +}
> +
> +int __init thunder_uncore_setup(struct thunder_uncore *uncore, int device_id,
> +				struct pmu *pmu, int counters)
> +{
> +	unsigned int vendor_id = PCI_VENDOR_ID_CAVIUM;
> +	struct thunder_uncore_unit  *unit, *tmp;
> +	struct thunder_uncore_node *node;
> +	struct pci_dev *pdev = NULL;
> +	int ret, node_id, found = 0;
> +
> +	/* detect PCI devices */
> +	while ((pdev = pci_get_device(vendor_id, device_id, pdev))) {

Redundant brackets?

> +		if (!pdev)
> +			break;

Redundant check?

> +		node_id = dev_to_node(&pdev->dev);
> +
> +		/* allocate node if necessary */
> +		if (!uncore->nodes[node_id])
> +			uncore->nodes[node_id] = alloc_node(uncore, node_id, counters);
> +
> +		node = uncore->nodes[node_id];
> +		if (!node) {
> +			ret = -ENOMEM;
> +			goto fail;
> +		}
> +
> +		unit = kzalloc(sizeof(*unit), GFP_KERNEL);
> +		if (!unit) {
> +			ret = -ENOMEM;
> +			goto fail;
> +		}
> +
> +		unit->pdev = pdev;
> +		unit->map = ioremap(pci_resource_start(pdev, 0),
> +				    pci_resource_len(pdev, 0));
> +		list_add(&unit->entry, &node->unit_list);
> +		node->nr_units++;
> +		found++;
> +	}
> +
> +	if (!found)
> +		return -ENODEV;
> +
> +	cpuhp_state_add_instance_nocalls(CPUHP_AP_UNCORE_CAVIUM_ONLINE,
> +                                         &uncore->node);
> +
> +	/*
> +	 * perf PMU is CPU dependent in difference to our uncore devices.
> +	 * Just pick a CPU and migrate away if it goes offline.
> +	 */
> +	cpumask_set_cpu(smp_processor_id(), &uncore->active_mask);
> +
> +	uncore->pmu = *pmu;
> +	ret = perf_pmu_register(&uncore->pmu, uncore->pmu.name, -1);
> +	if (ret)
> +		goto fail;
> +
> +	return 0;
> +
> +fail:
> +	node_id = 0;
> +	while (uncore->nodes[node_id]) {
> +		node = uncore->nodes[node_id];
> +
> +		list_for_each_entry_safe(unit, tmp, &node->unit_list, entry) {

Why do you need the _safe variant?

Will