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

[Ping Gan <jacky_gam_2001@163.com>]

> 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.

I don't fully understand what you said 'by default'. Did you mean we 
should just remove 'unbounded' parameter and create workqueue by 
WQ_UNBOUND flag or besides that, we should also add other parameter 
to switch 'unbounded' workqueue  to 'bounded' workqueue?

Thanks,
Ping