Messages in this thread | | | Date | Mon, 9 Sep 2019 20:50:35 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH] driver core: ensure a device has valid node id in device_add() |
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On Mon 09-09-19 14:04:23, Yunsheng Lin wrote: > Currently a device does not belong to any of the numa nodes > (dev->numa_node is NUMA_NO_NODE) when the node id is neither > specified by fw nor by virtual device layer and the device has > no parent device. > > According to discussion in [1]:
Please do not reference important parts of the justification via a link. Just quote the relevant part to the changelog. It is just too easy that external links die - not to mention lkml.org.
> Even if a device's numa node is not specified, the device really > does belong to a node.
What does this mean?
> This patch sets the device node to node 0 in device_add() if the > device's node id is not specified and it either has no parent > device, or the parent device also does not have a valid node id.
Why is node 0 special? I have seen platforms with node 0 missing or being memory less. The changelog also lacks an actual problem descripton. Why do we even care about NUMA_NO_NODE? E.g. the page allocator interprets NUMA_NO_NODE as the closest node with a memory. And by closest it really means to the CPU which is performing the allocation.
> [1] https://lkml.org/lkml/2019/9/2/466 > > Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com> > --- > Changelog RFC -> v1: > 1. Drop log error message and use a "if" instead of "? :". > 2. Drop the RFC tag. > --- > drivers/base/core.c | 10 +++++++--- > include/linux/numa.h | 2 ++ > 2 files changed, 9 insertions(+), 3 deletions(-) > > diff --git a/drivers/base/core.c b/drivers/base/core.c > index 1669d41..f79ad20 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -2107,9 +2107,13 @@ int device_add(struct device *dev) > if (kobj) > dev->kobj.parent = kobj; > > - /* use parent numa_node */ > - if (parent && (dev_to_node(dev) == NUMA_NO_NODE)) > - set_dev_node(dev, dev_to_node(parent)); > + /* use parent numa_node or default node 0 */ > + if (!numa_node_valid(dev_to_node(dev))) { > + if (parent && numa_node_valid(dev_to_node(parent))) > + set_dev_node(dev, dev_to_node(parent)); > + else > + set_dev_node(dev, 0); > + } > > /* first, register with generic layer. */ > /* we require the name to be set before, and pass NULL */ > diff --git a/include/linux/numa.h b/include/linux/numa.h > index 110b0e5..eccc757 100644 > --- a/include/linux/numa.h > +++ b/include/linux/numa.h > @@ -13,4 +13,6 @@ > > #define NUMA_NO_NODE (-1) > > +#define numa_node_valid(node) ((unsigned int)(node) < nr_node_ids) > + > #endif /* _LINUX_NUMA_H */ > -- > 2.8.1
-- Michal Hocko SUSE Labs
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