From: Andrew Morton <akpm@linux-foundation.org>
To: Donet Tom <donettom@linux.ibm.com>
Cc: David Hildenbrand <david@kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Ritesh Harjani <ritesh.list@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Ying Huang <huang.ying.caritas@gmail.com>,
Juri Lelli <juri.lelli@redhat.com>, Mel Gorman <mgorman@suse.de>
Subject: Re: [PATCH] memory tiering: Do not allow promotion if NUMA_BALANCING_MEMORY_TIERING is disabled
Date: Fri, 20 Mar 2026 09:20:29 -0700 [thread overview]
Message-ID: <20260320092029.7b2e2a9f24bfd5197541223e@linux-foundation.org> (raw)
In-Reply-To: <20260320092251.1290207-1-donettom@linux.ibm.com>
On Fri, 20 Mar 2026 14:52:51 +0530 Donet Tom <donettom@linux.ibm.com> wrote:
> In the current implementation, if NUMA_BALANCING_MEMORY_TIERING is
> disabled and the pages are on the lower tier, the pages may still be
> promoted.
>
> This happens because task_numa_work() updates the last_cpupid field to
> record the last access time only when NUMA_BALANCING_MEMORY_TIERING is
> enabled and the folio is on the lower tier. If
> NUMA_BALANCING_MEMORY_TIERING is disabled, the last_cpupid field
> retains a valid last CPU id.
>
> In should_numa_migrate_memory(), the decision checks whether
> NUMA_BALANCING_MEMORY_TIERING is disabled, the folio is on the lower
> tier, and last_cpupid is invalid. However, since last_cpupid remains
> valid when NUMA_BALANCING_MEMORY_TIERING is disabled, the condition
> evaluates to false and migration is allowed.
>
> This patch prevents promotion when NUMA_BALANCING_MEMORY_TIERING is
> disabled and the folio is on the lower tier.
Thanks. The AI reviewbot asked some questions:
https://sashiko.dev/#/patchset/20260320092251.1290207-1-donettom@linux.ibm.com
next prev parent reply other threads:[~2026-03-20 16:20 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-20 9:22 Donet Tom
2026-03-20 16:20 ` Andrew Morton [this message]
2026-03-21 12:16 ` Donet Tom
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