Re: [dpdk-dev] [PATCH] eal: change max hugepage sizes to 4

[David Marchand <david.marchand@redhat.com>]

On Wed, Aug 7, 2019 at 3:28 PM Hemant Agrawal <hemant.agrawal@nxp.com> wrote:
>
> HI Thomas,
>
> > > > DPDK currently is supporting maximum 3 hugepage, sizes whereas
> > > > system can support more than this e.g.
> > > > 64K, 2M, 32M and 1G.
> > >
> > > You can mention ARM platform here, and that this issue starts with
> > > kernel 5.2 (and I would try to mention this in the title as well).
> > > This is better than an annotation that will be lost.
> > >
> > >
> > > > Having these four hugepage sizes available to use by DPDK, which is
> > > > valid in case of '--in-memory' EAL option or using 4 separate mount
> > > > points for each hugepage size;
> > > > hugepage_info_init() API reports an error.
> > >
> > > Can you describe what is the impact from a user point of view rather
> > > than mentioning this internal function?
> >
> > Yes please, we need to understand how much it is critical.
> > Should we Cc stable@dpdk.org for backport?
> > Should it be merged at the last minute in 19.08?
> >
>
> VPP usages in-memory option. So, VPP on ARM with kernel 5.2 wont' work without this patch.
>

I have been looking at the changes in the linux kernel.
Can you pinpoint at the commit that changed this in 5.2?

I can see a change in the code, but in 5.0, or maybe something changed
in the configuration.

The patch you propose is not that risky (x86 supports two pagesizes,
and max hugepage is already at 3, so we know the code works fine with
less than the max).
Yet, I want to understand why this is urgent now.

CCing other architecture maintainers.


-- 
David Marchand