Re: [PATCH 0/3] blk-mq & nvme: introduce .map_changed
From: Keith Busch
Date: Tue Sep 29 2015 - 10:26:21 EST
On Mon, 28 Sep 2015, Ming Lei wrote:
This patchset introduces .map_changed callback into 'struct blk_mq_ops',
and use this callback to get NVMe notified about the mapping changed event,
then NVMe can update the irq affinity hint for its queues.
I think this is going the wrong direction. Shouldn't we provide blk-mq
the vectors in the tag set so that layer can manage the irq hints?
This could lead to more cpu-queue assignment optimizations from using
that information. For example, two h/w contexts sharing the same vector
shouldn't be assigned to cpus on different NUMA nodes.
Also the 'cpumask' in 'struct blk_mq_tags' isn't needed any more, so remove
that and related kernel interface.
It was added to the tags because the cpu mask is an artifact of the
tags rather that duplicating it across all the h/w contexts sharing the
same set. It also doesn't let a h/w context from one namespace overwrite
another's cpu affinity mask when they share the same vector.
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