diff mbox series

[RFC,1/4] drivers/nvdimm: Add perf interface to expose nvdimm performance stats

Message ID 20210512163824.255370-2-kjain@linux.ibm.com (mailing list archive)
State New
Headers show
Series Add perf interface to expose nvdimm performance stats | expand

Commit Message

Kajol Jain May 12, 2021, 4:38 p.m. UTC
Patch adds performance stats reporting support for nvdimm.
Added interface includes support for a pmu register function and
callbacks to be used by the arch/platform specific drivers.
User could use the standard perf tool to access perf events exposed
via pmu.

A structure is added called nvdimm_pmu which can be used to add
platform specific data like supported events and callbacks to pmu
functions like event_init/add/delete/read. It also adds
unregister_nvdimm_pmu function to handle unregistering of a pmu device.

Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
---
 drivers/nvdimm/Makefile  |   1 +
 drivers/nvdimm/nd_perf.c | 111 +++++++++++++++++++++++++++++++++++++++
 include/linux/nd.h       |  31 +++++++++++
 3 files changed, 143 insertions(+)
 create mode 100644 drivers/nvdimm/nd_perf.c

Comments

Peter Zijlstra May 12, 2021, 5:27 p.m. UTC | #1
On Wed, May 12, 2021 at 10:08:21PM +0530, Kajol Jain wrote:
> +static void nvdimm_pmu_read(struct perf_event *event)
> +{
> +	struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
> +
> +	/* jump to arch/platform specific callbacks if any */
> +	if (nd_pmu && nd_pmu->read)
> +		nd_pmu->read(event, nd_pmu->dev);
> +}
> +
> +static void nvdimm_pmu_del(struct perf_event *event, int flags)
> +{
> +	struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
> +
> +	/* jump to arch/platform specific callbacks if any */
> +	if (nd_pmu && nd_pmu->del)
> +		nd_pmu->del(event, flags, nd_pmu->dev);
> +}
> +
> +static int nvdimm_pmu_add(struct perf_event *event, int flags)
> +{
> +	struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
> +
> +	if (flags & PERF_EF_START)
> +		/* jump to arch/platform specific callbacks if any */
> +		if (nd_pmu && nd_pmu->add)
> +			return nd_pmu->add(event, flags, nd_pmu->dev);
> +	return 0;
> +}

What's the value add here? Why can't you directly set driver pointers? I
also don't really believe ->{add,del,read} can be optional and still
have a sane driver.
Kajol Jain May 13, 2021, 12:26 p.m. UTC | #2
On 5/12/21 10:57 PM, Peter Zijlstra wrote:
> On Wed, May 12, 2021 at 10:08:21PM +0530, Kajol Jain wrote:
>> +static void nvdimm_pmu_read(struct perf_event *event)
>> +{
>> +	struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
>> +
>> +	/* jump to arch/platform specific callbacks if any */
>> +	if (nd_pmu && nd_pmu->read)
>> +		nd_pmu->read(event, nd_pmu->dev);
>> +}
>> +
>> +static void nvdimm_pmu_del(struct perf_event *event, int flags)
>> +{
>> +	struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
>> +
>> +	/* jump to arch/platform specific callbacks if any */
>> +	if (nd_pmu && nd_pmu->del)
>> +		nd_pmu->del(event, flags, nd_pmu->dev);
>> +}
>> +
>> +static int nvdimm_pmu_add(struct perf_event *event, int flags)
>> +{
>> +	struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
>> +
>> +	if (flags & PERF_EF_START)
>> +		/* jump to arch/platform specific callbacks if any */
>> +		if (nd_pmu && nd_pmu->add)
>> +			return nd_pmu->add(event, flags, nd_pmu->dev);
>> +	return 0;
>> +}
> 
> What's the value add here? Why can't you directly set driver pointers? I
> also don't really believe ->{add,del,read} can be optional and still
> have a sane driver.
> 

Hi Peter,

  The intend for adding these callbacks  is to give flexibility to the
arch/platform specific driver code to use its own routine for getting 
counter data or specific checks/operations. Arch/platform driver code
would have different method to get the counter data like IBM pseries
nmem* device which uses a hypervisor call(hcall).

But yes the current read/add/del functions are not adding value. We
could  add an arch/platform specific function which could handle the
capturing of the counter data and do the rest of the operation here,
is this approach better?

Thanks,
Kajol Jain
Peter Zijlstra May 14, 2021, 11:47 a.m. UTC | #3
On Thu, May 13, 2021 at 05:56:14PM +0530, kajoljain wrote:

> But yes the current read/add/del functions are not adding value. We
> could  add an arch/platform specific function which could handle the
> capturing of the counter data and do the rest of the operation here,
> is this approach better?

Right; have your register_nvdimm_pmu() set pmu->{add,del,read} to
nd_pmu->{add,del,read} directly, don't bother with these intermediates.
Also you can WARN_ON_ONCE() if any of them are NULL and fail
registration at that point.
Kajol Jain May 17, 2021, 6:43 a.m. UTC | #4
On 5/14/21 5:17 PM, Peter Zijlstra wrote:
> On Thu, May 13, 2021 at 05:56:14PM +0530, kajoljain wrote:
> 
>> But yes the current read/add/del functions are not adding value. We
>> could  add an arch/platform specific function which could handle the
>> capturing of the counter data and do the rest of the operation here,
>> is this approach better?
> 
> Right; have your register_nvdimm_pmu() set pmu->{add,del,read} to
> nd_pmu->{add,del,read} directly, don't bother with these intermediates.
> Also you can WARN_ON_ONCE() if any of them are NULL and fail
> registration at that point.
> 

Hi Peter,
    I will make all required changes and send next version of this patchset soon.

Thanks,
Kajol Jain
diff mbox series

Patch

diff --git a/drivers/nvdimm/Makefile b/drivers/nvdimm/Makefile
index 29203f3d3069..25dba6095612 100644
--- a/drivers/nvdimm/Makefile
+++ b/drivers/nvdimm/Makefile
@@ -18,6 +18,7 @@  nd_e820-y := e820.o
 libnvdimm-y := core.o
 libnvdimm-y += bus.o
 libnvdimm-y += dimm_devs.o
+libnvdimm-y += nd_perf.o
 libnvdimm-y += dimm.o
 libnvdimm-y += region_devs.o
 libnvdimm-y += region.o
diff --git a/drivers/nvdimm/nd_perf.c b/drivers/nvdimm/nd_perf.c
new file mode 100644
index 000000000000..d28bec2b61a2
--- /dev/null
+++ b/drivers/nvdimm/nd_perf.c
@@ -0,0 +1,111 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * nd_perf.c: NVDIMM Device Performance Monitoring Unit support
+ *
+ * Perf interface to expose nvdimm performance stats.
+ *
+ * Copyright (C) 2021 IBM Corporation
+ */
+
+#define pr_fmt(fmt) "nvdimm_pmu: " fmt
+
+#include <linux/nd.h>
+
+#define to_nvdimm_pmu(_pmu)	container_of(_pmu, struct nvdimm_pmu, pmu)
+
+static int nvdimm_pmu_event_init(struct perf_event *event)
+{
+	struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
+
+	/* test the event attr type for PMU enumeration */
+	if (event->attr.type != event->pmu->type)
+		return -ENOENT;
+
+	/* it does not support event sampling mode */
+	if (is_sampling_event(event))
+		return -EINVAL;
+
+	/* no branch sampling */
+	if (has_branch_stack(event))
+		return -EOPNOTSUPP;
+
+	/* jump to arch/platform specific callbacks if any */
+	if (nd_pmu && nd_pmu->event_init)
+		return nd_pmu->event_init(event, nd_pmu->dev);
+
+	return 0;
+}
+
+static void nvdimm_pmu_read(struct perf_event *event)
+{
+	struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
+
+	/* jump to arch/platform specific callbacks if any */
+	if (nd_pmu && nd_pmu->read)
+		nd_pmu->read(event, nd_pmu->dev);
+}
+
+static void nvdimm_pmu_del(struct perf_event *event, int flags)
+{
+	struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
+
+	/* jump to arch/platform specific callbacks if any */
+	if (nd_pmu && nd_pmu->del)
+		nd_pmu->del(event, flags, nd_pmu->dev);
+}
+
+static int nvdimm_pmu_add(struct perf_event *event, int flags)
+{
+	struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
+
+	if (flags & PERF_EF_START)
+		/* jump to arch/platform specific callbacks if any */
+		if (nd_pmu && nd_pmu->add)
+			return nd_pmu->add(event, flags, nd_pmu->dev);
+	return 0;
+}
+
+int register_nvdimm_pmu(struct nvdimm_pmu *nd_pmu, struct platform_device *pdev)
+{
+	int rc;
+
+	if (!nd_pmu || !pdev)
+		return -EINVAL;
+
+	nd_pmu->pmu.task_ctx_nr = perf_invalid_context;
+	nd_pmu->pmu.event_init = nvdimm_pmu_event_init;
+	nd_pmu->pmu.add = nvdimm_pmu_add;
+	nd_pmu->pmu.del = nvdimm_pmu_del;
+	nd_pmu->pmu.read = nvdimm_pmu_read;
+	nd_pmu->pmu.name = nd_pmu->name;
+	nd_pmu->pmu.attr_groups = nd_pmu->attr_groups;
+	nd_pmu->pmu.capabilities = PERF_PMU_CAP_NO_INTERRUPT |
+				PERF_PMU_CAP_NO_EXCLUDE;
+
+	/*
+	 * Adding platform_device->dev pointer to nvdimm_pmu, so that we can
+	 * access that device data in PMU callbacks and also pass it to
+	 * arch/platform specific code.
+	 */
+	nd_pmu->dev = &pdev->dev;
+
+	rc = perf_pmu_register(&nd_pmu->pmu, nd_pmu->name, -1);
+	if (rc)
+		return rc;
+
+	pr_info("%s NVDIMM performance monitor support registered\n",
+		nd_pmu->name);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(register_nvdimm_pmu);
+
+void unregister_nvdimm_pmu(struct pmu *nd_pmu)
+{
+	/*
+	 * nd_pmu will get free in arch/platform specific code once
+	 * corresponding pmu get unregistered.
+	 */
+	perf_pmu_unregister(nd_pmu);
+}
+EXPORT_SYMBOL_GPL(unregister_nvdimm_pmu);
diff --git a/include/linux/nd.h b/include/linux/nd.h
index ee9ad76afbba..fa6e60b2b368 100644
--- a/include/linux/nd.h
+++ b/include/linux/nd.h
@@ -8,6 +8,8 @@ 
 #include <linux/ndctl.h>
 #include <linux/device.h>
 #include <linux/badblocks.h>
+#include <linux/platform_device.h>
+#include <linux/perf_event.h>
 
 enum nvdimm_event {
 	NVDIMM_REVALIDATE_POISON,
@@ -23,6 +25,35 @@  enum nvdimm_claim_class {
 	NVDIMM_CCLASS_UNKNOWN,
 };
 
+/**
+ * struct nvdimm_pmu - data structure for nvdimm perf driver
+ *
+ * @name: name of the nvdimm pmu device.
+ * @pmu: pmu data structure for nvdimm performance stats.
+ * @cpu: designated cpu for counter access.
+ * @dev: nvdimm device pointer.
+ * @functions(event_init/add/del/read): platform specific callbacks.
+ * @attr_groups: data structure for events/formats/cpumask.
+ * @node: node for cpu hotplug notifier link.
+ * @cpuhp_state: state for cpu hotplug notification.
+ */
+struct nvdimm_pmu {
+	const char *name;
+	struct pmu pmu;
+	int cpu;
+	struct device *dev;
+	int (*event_init)(struct perf_event *event,  struct device *dev);
+	int  (*add)(struct perf_event *event, int flags, struct device *dev);
+	void (*del)(struct perf_event *event, int flags, struct device *dev);
+	void (*read)(struct perf_event *event,  struct device *dev);
+	const struct attribute_group **attr_groups;
+	struct hlist_node node;
+	enum cpuhp_state cpuhp_state;
+};
+
+int register_nvdimm_pmu(struct nvdimm_pmu *nvdimm, struct platform_device *pdev);
+void unregister_nvdimm_pmu(struct pmu *pmu);
+
 struct nd_device_driver {
 	struct device_driver drv;
 	unsigned long type;