Re: [PATCH 0/2] nvmet: support polling task for RDMA and TCP
From: Sagi Grimberg
Date: Sun Jun 30 2024 - 04:59:07 EST
Hey Ping Gan,
On 26/06/2024 11:28, Ping Gan wrote:
When running nvmf on SMP platform, current nvme target's RDMA and
TCP use kworker to handle IO. But if there is other high workload
in the system(eg: on kubernetes), the competition between the
kworker and other workload is very radical. And since the kworker
is scheduled by OS randomly, it's difficult to control OS resource
and also tune the performance. If target support to use delicated
polling task to handle IO, it's useful to control OS resource and
gain good performance. So it makes sense to add polling task in
rdma-rdma and rdma-tcp modules.
This is NOT the way to go here.
Both rdma and tcp are driven from workqueue context, which are bound
workqueues.
So there are two ways to go here:
1. Add generic port cpuset and use that to direct traffic to the
appropriate set of cores
(i.e. select an appropriate comp_vector for rdma and add an appropriate
steering rule
for tcp).
2. Add options to rdma/tcp to use UNBOUND workqueues, and allow users to
control
these UNBOUND workqueues cpumask via sysfs.
(2) will not control interrupts to steer to other workloads cpus, but
the handlers may
run on a set of dedicated cpus.
(1) is a better solution, but harder to implement.
You also should look into nvmet-fc as well (and nvmet-loop for that matter).