linux-kernel - Re: fd3e45436660 ("ACPI / NUMA: ia64: Parse all entries of SRAT memory affinity table")

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Date:   Wed, 9 May 2018 14:56:11 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Ganapatrao Kulkarni <gklkml16@...il.com>
Cc:     Ganapatrao Kulkarni <ganapatrao.kulkarni@...ium.com>,
        Tony Luck <tony.luck@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        tiantao6@...wei.com, LKML <linux-kernel@...r.kernel.org>,
        linux-acpi@...r.kernel.org
Subject: Re: fd3e45436660 ("ACPI / NUMA: ia64: Parse all entries of SRAT
 memory affinity table")

On Wed 09-05-18 18:07:16, Ganapatrao Kulkarni wrote:
> Hi Michal
> 
> 
> On Wed, May 9, 2018 at 5:54 PM, Michal Hocko <mhocko@...nel.org> wrote:
> > On Wed 11-04-18 12:48:32, Michal Hocko wrote:
> >> Hi,
> >> my attention was brought to the %subj commit and either I am missing
> >> something or the patch is quite dubious. What is it actually trying to
> >> fix? If a BIOS/FW provides more memblocks than the limit then we would
> >> get misleading numa topology (numactl -H output) but is the situation
> >> much better with it applied? Numa init code will refuse to init more
> >> memblocks than the limit and falls back to dummy_numa_init (AFAICS)
> >> which will break the topology again and numactl -H will have a
> >> misleading output anyway.
> 
> IIRC, the MEMBLOCK beyond max limit getting dropped from visible
> memory(partial drop from a node).
> this patch removed any upper limit on memblocks and allowed to parse
> all entries of SRAT.

Yeah I've understood that much. My question is, however, why do we care
about parsing the NUMA topology when we fallback into a single NUMA node
anyway? Or do I misunderstand the code? I do not have any platform with
that many memblocks.

-- 
Michal Hocko
SUSE Labs