linux-kernel - Re: [PATCH rdma-next 2/7] RDMA/mlx5: Replace cache list with Xarray

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Message-ID: <20211209175616.GV6385@nvidia.com>
Date:   Thu, 9 Dec 2021 13:56:16 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Aharon Landau <aharonl@...dia.com>
Cc:     Leon Romanovsky <leon@...nel.org>, linux-kernel@...r.kernel.org,
        linux-rdma@...r.kernel.org
Subject: Re: [PATCH rdma-next 2/7] RDMA/mlx5: Replace cache list with Xarray

On Thu, Dec 09, 2021 at 10:21:22AM +0200, Aharon Landau wrote:

> > It feels like pending and (reserved - stored) are really the same
> > thing, so maybe just directly limit the number of reserved and test it
> > after
> The mlx5_ib_dereg_mr is reserving entries as well. Should I limit
> create_mkey_cb due to pending deregs?

Sure, it is the same concept, deregs are going to refill things just
as wass as new creations.

> > > @@ -287,39 +318,37 @@ static void remove_cache_mr_locked(struct mlx5_cache_ent *ent)
> > >   {
> > >   	struct mlx5_ib_mr *mr;
> > > -	lockdep_assert_held(&ent->lock);
> > > -	if (list_empty(&ent->head))
> > > +	if (!ent->stored)
> > >   		return;
> > > -	mr = list_first_entry(&ent->head, struct mlx5_ib_mr, list);
> > > -	list_del(&mr->list);
> > > -	ent->available_mrs--;
> > > +	mr = __xa_store(&ent->mkeys, --ent->stored, NULL, GFP_KERNEL);
> > > +	WARN_ON(mr == NULL || xa_is_err(mr));
> > Add a if (reserved != stored)  before the below?
> I initiated the xarray using XA_FLAGS_ALLOC, therefore, the __xa_store above
> will mark the entry as ZERO_ENTRY.

Oh, do not use XA_FLAGS_ALLOC, this is not what is it for

Jason