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SubjectRe: [PATCH v4 5/5] nvdimm: Schedule device registration on node local to the device
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On 9/20/2018 3:59 PM, Dan Williams wrote:
> On Thu, Sep 20, 2018 at 3:31 PM Alexander Duyck
> <alexander.h.duyck@linux.intel.com> wrote:
>>
>> This patch is meant to force the device registration for nvdimm devices to
>> be closer to the actual device. This is achieved by using either the NUMA
>> node ID of the region, or of the parent. By doing this we can have
>> everything above the region based on the region, and everything below the
>> region based on the nvdimm bus.
>>
>> One additional change I made is that we hold onto a reference to the parent
>> while we are going through registration. By doing this we can guarantee we
>> can complete the registration before we have the parent device removed.
>>
>> By guaranteeing NUMA locality I see an improvement of as high as 25% for
>> per-node init of a system with 12TB of persistent memory.
>>
>> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
>> ---
>> drivers/nvdimm/bus.c | 19 +++++++++++++++++--
>> 1 file changed, 17 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
>> index 8aae6dcc839f..ca935296d55e 100644
>> --- a/drivers/nvdimm/bus.c
>> +++ b/drivers/nvdimm/bus.c
>> @@ -487,7 +487,9 @@ static void nd_async_device_register(void *d, async_cookie_t cookie)
>> dev_err(dev, "%s: failed\n", __func__);
>> put_device(dev);
>> }
>> +
>> put_device(dev);
>> + put_device(dev->parent);
>
> Good catch. The child does not pin the parent until registration, but
> we need to make sure the parent isn't gone while were waiting for the
> registration work to run.
>
> Let's break this reference count fix out into its own separate patch,
> because this looks to be covering a gap that may need to be
> recommended for -stable.

Okay, I guess I can do that.

>
>>
>> static void nd_async_device_unregister(void *d, async_cookie_t cookie)
>> @@ -504,12 +506,25 @@ static void nd_async_device_unregister(void *d, async_cookie_t cookie)
>>
>> void __nd_device_register(struct device *dev)
>> {
>> + int node;
>> +
>> if (!dev)
>> return;
>> +
>> dev->bus = &nvdimm_bus_type;
>> + get_device(dev->parent);
>> get_device(dev);
>> - async_schedule_domain(nd_async_device_register, dev,
>> - &nd_async_domain);
>> +
>> + /*
>> + * For a region we can break away from the parent node,
>> + * otherwise for all other devices we just inherit the node from
>> + * the parent.
>> + */
>> + node = is_nd_region(dev) ? to_nd_region(dev)->numa_node :
>> + dev_to_node(dev->parent);
>
> Devices already automatically inherit the node of their parent, so I'm
> not understanding why this is needed?

That doesn't happen until you call device_add, which you don't call
until nd_async_device_register. All that has been called on the device
up to now is device_initialize which leaves the node at NUMA_NO_NODE.

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