Re: [PATCH v2 0/2] nvmet: support unbound_wq for RDMA and TCP

[Sagi Grimberg]

On 19/07/2024 9:28, Hannes Reinecke wrote:
> On 7/19/24 07:31, Christoph Hellwig wrote:
> > On Wed, Jul 17, 2024 at 05:14:49PM +0800, Ping Gan wrote:
> > > When running nvmf on SMP platform, current nvme target's RDMA and
> > > TCP use bounded workqueue to handle IO, but when there is other high
> > > workload on the system(eg: kubernetes), the competition between the
> > > bounded kworker and other workload is very radical. To decrease the
> > > resource race of OS among them, this patchset will enable unbounded
> > > workqueue for nvmet-rdma and nvmet-tcp; besides that, it can also
> > > get some performance improvement. And this patchset bases on previous
> > > discussion from below session.
> >
> > So why aren't we using unbound workqueues by default?  Who makea the
> > policy decision and how does anyone know which one to chose?
> I'd be happy to switch to unbound workqueues per default.
> It actually might be a left over from the various workqueue changes;
> at one point 'unbound' meant that effectively only one CPU was used
> for the workqueue, and you had to remove the 'unbound' parameter to
> have the workqueue run on all CPUs. That has since changed, so I guess
> switching to unbound per default is the better option here.

A guess needs to be based with supporting data if we want to have this 
change.