Subject: Re: [PATCH rdma-next v1 07/11] RDMA/nldev: Allow optional-counter status configuration through RDMA netlink

From: Leon Romanovsky <[email-masked]>
Date: Wed, 29 Sep 2021 15:27:39 +0300

On Mon, Sep 27, 2021 at 02:20:06PM -0300, Jason Gunthorpe wrote:
> On Wed, Sep 15, 2021 at 02:07:26AM +0300, Leon Romanovsky wrote:
> > -		return -EINVAL;
> > +		need_enable = false;
> > +		disabled = test_bit(i, stats->is_disabled);
> > +		nla_for_each_nested(entry_attr,
> > +				    tb[RDMA_NLDEV_ATTR_STAT_HWCOUNTERS], rem) {
> > +			index = nla_get_u32(entry_attr);
> > +			if (index >= stats->num_counters)
> > +				return -EINVAL;
> > +			if (i == index) {
> > +				need_enable = true;
> > +				break;
> > +			}
> > +		}
> >  
> > -	port = nla_get_u32(tb[RDMA_NLDEV_ATTR_PORT_INDEX]);
> > -	if (!rdma_is_port_valid(device, port)) {
> > -		ret = -EINVAL;
> > -		goto err;
> > +		if (disabled && need_enable)
> > +			ret = rdma_counter_modify(device, port, i, true);
> > +		else if (!disabled && !need_enable)
> > +			ret = rdma_counter_modify(device, port, i, false);
> 
> This disabled check looks racy, I would do the no-change optimization inside
> rdma_counter_modify()
> 
> Also, this is a O(N^2) algorithm, why not do it in one pass with a
> small memory allocation for the target state bitmap?

We don't have many counters. Is this optimization really worth it?

Thanks

> Jason