Re: [PATCH] ia64: Ensure proper NUMA distance and possible map initialization
- To: Valentin Schneider <valentin.schneider@arm.com>
- Cc: linux-kernel@vger.kernel.org, "linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>, debian-ia64 <debian-ia64@lists.debian.org>, John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>, "Peter Zijlstra (Intel)" <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>, Vincent Guittot <vincent.guittot@linaro.org>, Dietmar Eggemann <dietmar.eggemann@arm.com>, Sergei Trofimovich <slyfox@gentoo.org>, Anatoly Pugachev <matorola@gmail.com>
- Subject: Re: [PATCH] ia64: Ensure proper NUMA distance and possible map initialization
- From: Andrew Morton <akpm@linux-foundation.org>
- Date: Wed, 24 Mar 2021 11:54:32 -0700
- Message-id: <[🔎] 20210324115432.4102cd93d35a2edb1742dec7@linux-foundation.org>
- In-reply-to: <[🔎] 20210318130617.896309-1-valentin.schneider@arm.com>
- References: <[🔎] 20210318130617.896309-1-valentin.schneider@arm.com>
On Thu, 18 Mar 2021 13:06:17 +0000 Valentin Schneider <valentin.schneider@arm.com> wrote:
> John Paul reported a warning about bogus NUMA distance values spurred by
> commit:
>
> 620a6dc40754 ("sched/topology: Make sched_init_numa() use a set for the deduplicating sort")
>
> In this case, the afflicted machine comes up with a reported 256 possible
> nodes, all of which are 0 distance away from one another. This was
> previously silently ignored, but is now caught by the aforementioned
> commit.
>
> The culprit is ia64's node_possible_map which remains unchanged from its
> initialization value of NODE_MASK_ALL. In John's case, the machine doesn't
> have any SRAT nor SLIT table, but AIUI the possible map remains untouched
> regardless of what ACPI tables end up being parsed. Thus, !online &&
> possible nodes remain with a bogus distance of 0 (distances \in [0, 9] are
> "reserved and have no meaning" as per the ACPI spec).
>
> Follow x86 / drivers/base/arch_numa's example and set the possible map to
> the parsed map, which in this case seems to be the online map.
>
> Link: http://lore.kernel.org/r/255d6b5d-194e-eb0e-ecdd-97477a534441@physik.fu-berlin.de
> Fixes: 620a6dc40754 ("sched/topology: Make sched_init_numa() use a set for the deduplicating sort")
> Reported-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
> ---
> This might need an earlier Fixes: tag, but all of this is quite old and
> dusty (the git blame rabbit hole leads me to ~2008/2007)
>
Thanks. Is this worth a cc:stable tag?
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