nvme: NUMA locality for fabrics
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Cover letter [PATCHv3 0/3] nvme: NUMA locality for fabrics
Quoted 9 lines · Christoph Hellwig
Quoted 4 lines · Hannes Reinecke
Fully agreed here.
It all comes down to the link latency.
If the link latency is the main bottleneck multipathing will benefit from round-robin (or any I/O scheduler, for that matter).It still makes a lot more sense to try to have queues with an affinity to a given path rather than doing round robin IFF you care about latency.
Quoted 8 lines
If you latency sucks anyway round robing makes sense. But why do you use nvme on such a horrible interconnect anyway?
Quoted 3 lines
And this it not just relevant for 'legacy' hardware; I've seen a performance benefit on a 32G FC setup, which is pretty much state of the art currently.
Well, FC is legacy no matter which link speed.
Fabrics has a required Identify Controller field called "MAXCMD" which is a per-queue limiter. A sufficiently shallow value with a high queue depth workload could justify round-robin'ing your queues.