linux-kernel - Re: [PATCH rdma-next v4 4/4] RDMA/umem: Move to allocate SG table from pages

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Message-ID: <086a82d3-fd3a-7160-dba4-c7b223585b88@nvidia.com>
Date:   Wed, 30 Sep 2020 18:40:15 +0300
From:   Maor Gottlieb <maorg@...dia.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     Leon Romanovsky <leon@...nel.org>,
        Doug Ledford <dledford@...hat.com>,
        Christoph Hellwig <hch@....de>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        <dri-devel@...ts.freedesktop.org>,
        <intel-gfx@...ts.freedesktop.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        <linux-kernel@...r.kernel.org>, <linux-rdma@...r.kernel.org>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Roland Scheidegger <sroland@...are.com>,
        "Tvrtko Ursulin" <tvrtko.ursulin@...el.com>,
        VMware Graphics <linux-graphics-maintainer@...are.com>
Subject: Re: [PATCH rdma-next v4 4/4] RDMA/umem: Move to allocate SG table
 from pages


On 9/30/2020 6:14 PM, Jason Gunthorpe wrote:
> On Wed, Sep 30, 2020 at 06:05:15PM +0300, Maor Gottlieb wrote:
>> This is right only for the last iteration. E.g. in the first iteration in
>> case that there are more pages (left_pages), then we allocate
>> SG_MAX_SINGLE_ALLOC.  We don't know how many pages from the second iteration
>> will be squashed to the SGE from the first iteration.
> Well, it is 0 or 1 SGE's. Check if the first page is mergable and
> subtract one from the required length?
>
> I dislike this sg_mark_end() it is something that should be internal,
> IMHO.

I can move it to __sg_alloc_table_from_pages:

         sgt->nents = tmp_nents;
+ if (!left_pages)
+         sg_mark_end(s);
  out:
         return s;

>
> Jason