Re: [PATCH 1/2] RDMA/nldev: add resource summary max values for usage rate display

[Tao Cui <cuitao@kylinos.cn>]

在 2026/4/26 20:42, Leon Romanovsky 写道:
> On Thu, Apr 23, 2026 at 02:13:51PM +0800, Tao Cui wrote:
>> Add RDMA_NLDEV_ATTR_RES_SUMMARY_ENTRY_MAX netlink attribute to expose
>> device resource limits (max_qp, max_cq, max_mr, max_pd, max_srq) in
>> the resource summary alongside the existing current count. This allows
>> userspace tools like iproute2's rdma to display resource usage rates.
> 
> Historically, we try to avoid duplicating functionality, and this already
> exists in ibv_devinfo. What is the reason for adding it to rdmatool as well?
> 
Thanks for your review.

You're right that ibv_devinfo exposes these limits via the verbs API.
The motivation here is not to duplicate ibv_devinfo, but to make the
existing `rdma resource show` output more self-contained.

Currently `rdma resource show` displays current resource counts (curr),
but not the maximum limits. To compute usage rates, a user must
cross-reference two separate tools using different interfaces
(ibv_devinfo via verbs vs. rdma via netlink). This is especially
inconvenient for monitoring and automation use cases that rely on
netlink + JSON output.

By adding max alongside curr in the same resource summary entry, the
rdma tool can present a complete picture in one query, and userspace
can compute usage rates without querying two different interfaces.

That said, if you feel this doesn't justify the addition, I'm happy
to withdraw or adjust the approach. For example, an alternative would
be to not add a new netlink attribute and instead let userspace tools
do the cross-referencing, though I think the single-query approach
provides better usability.

>>
>> The new attribute is optional and backward compatible - old userspace
>> tools will simply ignore it.
>>
>> Signed-off-by: Tao Cui <cuitao@kylinos.cn>