Nicolas Morey-Chaisemartin 2d7888b2c4 RDMA/srp: Fix support for unpopulated and unbalanced NUMA nodes
commit 2b5715fc17 upstream.

The current code computes a number of channels per SRP target and spreads
them equally across all online NUMA nodes.  Each channel is then assigned
a CPU within this node.

In the case of unbalanced, or even unpopulated nodes, some channels do not
get a CPU associated and thus do not get connected.  This causes the SRP
connection to fail.

This patch solves the issue by rewriting channel computation and
allocation:

- Drop channel to node/CPU association as it had no real effect on
  locality but added unnecessary complexity.

- Tweak the number of channels allocated to reduce CPU contention when
  possible:
  - Up to one channel per CPU (instead of up to 4 by node)
  - At least 4 channels per node, unless ch_count module parameter is
    used.

Link: https://lore.kernel.org/r/9cb4d9d3-30ad-2276-7eff-e85f7ddfb411@suse.com
Signed-off-by: Nicolas Morey-Chaisemartin <nmoreychaisemartin@suse.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-20 10:43:43 +01:00
2021-03-17 17:06:37 +01:00

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