netdev - Re: [PATCH mlx5-next 3/4] net/mlx5: Decrease default mr cache size

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Date:   Wed, 27 Mar 2019 16:24:27 +0200
From:   Or Gerlitz <gerlitz.or@...il.com>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        RDMA mailing list <linux-rdma@...r.kernel.org>,
        Artemy Kovalyov <artemyko@...lanox.com>,
        Guy Levi <guyle@...lanox.com>,
        Haggai Eran <haggaie@...lanox.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Moni Shoua <monis@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        linux-netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH mlx5-next 3/4] net/mlx5: Decrease default mr cache size

On Wed, Mar 27, 2019 at 3:36 PM Leon Romanovsky <leon@...nel.org> wrote:
> On Wed, Mar 27, 2019 at 01:58:17PM +0200, Or Gerlitz wrote:
> > On Wed, Mar 27, 2019 at 1:41 PM Leon Romanovsky <leon@...nel.org> wrote:
> > > On Wed, Mar 27, 2019 at 12:07:54PM +0200, Or Gerlitz wrote:
> > > > On Tue, Mar 19, 2019 at 11:25 AM Leon Romanovsky <leon@...nel.org> wrote:
> > > > > From: Artemy Kovalyov <artemyko@...lanox.com>
> > > > >
> > > > > Delete initialization of high order entries in mr cache to decrease initial
> > > > > memory footprint. When required, the administrator can populate the
> > > > > entries with memory keys via the /sys interface.
> > > >
> > > > Please add here:
> > > >
> > > > This approach is very helpful to reduce the per HW function memory
> > > > footprint in environments such as VMs. Before the patch we see
> > > > consumption of 0.9GB per function and after the patch about 0.1GB

here it needs to be "per physical function" and not "per function"

> > > > Lets push it into stable kernels, a Fixes tag here will cause that
> > > > to happen more easily, so please consider that.

>>> I'll add it at the "apply" stage.

>> Just to make sure, by "add it" you mean the signatures, the text and
>> the Fixes that?

> Yes, of course.

thanks

>> Also, is there any reason not to eliminate the mr cache pre-population
>> all together?

> AFAIK, pre-populated cache helps MPI application to start faster and
> with out-of-box experience. Nobody seems to care enough to challenge
> this internal assumption.

I see, we are cutting here ~0.8GB so lets just do it and wonder on the
remaining 0.1GB later..

It would be good to push it into 5.1-rc so the fallout into stables
will start right away and
not only by 5.2 time - can we do that?