Re: [PATCH] dma/pool: do not complain if DMA pool is not allocated

Michal Hocko
2022-03-25T16:55:17Z

On Fri 25-03-22 17:48:56, Christoph Hellwig wrote:
> On Fri, Mar 25, 2022 at 01:58:42PM +0100, Michal Hocko wrote:
> > Dang, I have just realized that I have misread the boot log and it has
> > turned out that a674e48c5443 is covering my situation because the
> > allocation failure message says:
> >
> > Node 0 DMA free:0kB boost:0kB min:0kB low:0kB high:0kB reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:636kB managed:0kB mlocked:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
>
> As in your report is from a kernel that does not have a674e48c5443
> yet?

yes. I just mixed up the early boot messages and thought that DMA zone
ended up with a single page. That message was saying something else
though.

> > I thought there are only few pages in the managed by the DMA zone. This
> > is still theoretically possible so I think __GFP_NOWARN makes sense here
> > but it would require to change the patch description.
> >
> > Is this really worth it?
>
> In general I think for kernels where we need the pool and can't allocate
> it, a warning is very useful. We just shouldn't spew it when there is
> no need for the pool to start with.

Well, do we have any way to find that out during early boot?

--
Michal Hocko
SUSE Labs