Re: [patch/rfc/rft] sd: allocate request_queue on device's localnuma node

From: Bart Van Assche
Date: Tue Oct 23 2012 - 13:42:00 EST

On 10/23/12 18:52, Jeff Moyer wrote:
Bart Van Assche <bvanassche@xxxxxxx> writes:
Please keep in mind that a
single PCIe bus may have a minimal distance to more than one NUMA
node. See e.g. the diagram at the top of page 8 in
for a system diagram of a NUMA system where each PCIe bus has a
minimal distance to two different NUMA nodes.

That's an interesting configuration. I wonder what the numa_node sysfs
file contains for such systems--do you know? I'm not sure how we could
allow this to be user-controlled at probe time. Did you have a specific
mechanism in mind? Module parameters? Something else?

As far as I can see in drivers/pci/pci-sysfs.c the numa_node sysfs attribute contains a single number, even for a topology like the one described above.

With regard to user control of the numa node: I'm not sure how to solve this in general. But for the ib_srp driver this should be easy to do: SCSI host creation is triggered by sending a login string to a sysfs attribute ("add_target"). It wouldn't take much time to add a parameter to that login string that specifies the NUMA node.


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