Re: [PATCH 3/3] libnvdimm: Add sysfs numa_node to NVDIMM devices

[Dan Williams]

On Tue, Jun 2, 2015 at 6:01 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> On Tue, Jun 2, 2015 at 5:26 PM, Toshi Kani <toshi.kani@xxxxxx> wrote:
>> Since NVDIMMs are installed on memory slots, they expose the NUMA
>> topology of a platform.
>>
>> This patch adds support of sysfs 'numa_node' to the NVDIMM devices
>> under /sys/bus/nd/devices, such as regionN, namespaceN.0, and bttN.
>> When bttN is not set up, its numa_node returns -1 (NUMA_NO_NODE).
>> nmemN/numa_node always returns -1 for now since this device is for
>> dimm-ioctl message interface and has little use of NUMA.  It can be
>> enhanced later to set a valid value if necessary.
>>
>> Here is an example of numa_node values on a 2-socket system with
>> a single NVDIMM range on each socket.
>>   /sys/bus/nd/devices
>>   |-- btt0/numa_node:-1
>>   |-- btt1/numa_node:0
>>   |-- namespace0.0/numa_node:0
>>   |-- namespace1.0/numa_node:1
>>   |-- nmem0/numa_node:-1
>>   |-- nmem1/numa_node:-1
>>   |-- region0/numa_node:0
>>   |-- region1/numa_node:1
>>
>> With this change, numactl(8) accepts 'block:' and 'file:' paths of
>> pmem and btt devices as shown in the examples below.
>>   numactl --preferred block:pmem0 --show
>>   numactl --preferred file:/dev/pmem0s --show
>>
>> Signed-off-by: Toshi Kani <toshi.kani@xxxxxx>
>> ---
>>  drivers/acpi/nfit.c          |    2 ++
>>  drivers/nvdimm/btt.c         |    2 ++
>>  drivers/nvdimm/bus.c         |   12 ++++++++++++
>>  drivers/nvdimm/nd.h          |    1 +
>>  drivers/nvdimm/region.c      |    1 +
>>  drivers/nvdimm/region_devs.c |    1 +
>>  include/linux/libnvdimm.h    |    1 +
>>  7 files changed, 20 insertions(+)
>>
>> diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c
>> index 5731e4a..a255f3a 100644
>> --- a/drivers/acpi/nfit.c
>> +++ b/drivers/acpi/nfit.c
>> @@ -1255,6 +1255,8 @@ static int acpi_nfit_register_region(struct acpi_nfit_desc *acpi_desc,
>>         ndr_desc->res = &res;
>>         ndr_desc->provider_data = nfit_spa;
>>         ndr_desc->attr_groups = acpi_nfit_region_attribute_groups;
>> +       ndr_desc->numa_node = acpi_map_pxm_to_node(spa->proximity_domain);
>> +
>>         list_for_each_entry(nfit_memdev, &acpi_desc->memdevs, list) {
>>                 struct acpi_nfit_memory_map *memdev = nfit_memdev->memdev;
>>                 struct nd_mapping *nd_mapping;
>> diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
>> index 2d7ce9e..3b3e115 100644
>> --- a/drivers/nvdimm/btt.c
>> +++ b/drivers/nvdimm/btt.c
>> @@ -1369,6 +1369,8 @@ static int nd_btt_probe(struct device *dev)
>>                 rc = -ENOMEM;
>>                 goto err_btt;
>>         }
>> +
>> +       set_dev_node(dev, nd_region->numa_node);
>>         dev_set_drvdata(dev, btt);
>>
>>         return 0;
>> diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
>> index d8a1794..5c34e68 100644
>> --- a/drivers/nvdimm/bus.c
>> +++ b/drivers/nvdimm/bus.c
>> @@ -339,9 +339,21 @@ static ssize_t devtype_show(struct device *dev, struct device_attribute *attr,
>>  }
>>  static DEVICE_ATTR_RO(devtype);
>>
>> +#ifdef CONFIG_NUMA
>> +static ssize_t numa_node_show(struct device *dev, struct device_attribute *attr,
>> +               char *buf)
>> +{
>> +       return sprintf(buf, "%d\n", dev->numa_node);
>> +}
>> +DEVICE_ATTR_RO(numa_node);
>> +#endif
>> +
>>  static struct attribute *nd_device_attributes[] = {
>>         &dev_attr_modalias.attr,
>>         &dev_attr_devtype.attr,
>> +#ifdef CONFIG_NUMA
>> +       &dev_attr_numa_node.attr,
>> +#endif
>>         NULL,
>>  };
>
> I'd prefer you define is_visible() in the nd_device_attribute_group
> and gate showing this attribute on IS_ENABLED(CONFIG_NUMA) rather than
> including these ifdef guards.  The ifdef guards aren't necessary in
> the CONFIG_NUMA=n case.

I also think is_visible() should hide this attribute on is_nvdimm() devices.
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