From: Andrew Morton <akpm@linux-foundation.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Sean Christopherson <seanjc@google.com>,
Yan Zhao <yan.y.zhao@intel.com>,
pbonzini@redhat.com, David Hildenbrand <david@kernel.org>,
Zi Yan <ziy@nvidia.com>, Matthew Brost <matthew.brost@intel.com>,
Joshua Hahn <joshua.hahnjy@gmail.com>,
Rakie Kim <rakie.kim@sk.com>, Byungchul Park <byungchul@sk.com>,
Gregory Price <gourry@gourry.net>,
Ying Huang <ying.huang@linux.alibaba.com>,
Alistair Popple <apopple@nvidia.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Neha Gholkar <nehagholkar@gmail.com>,
kvm@vger.kernel.org, rick.p.edgecombe@intel.com,
vishal.l.verma@intel.com
Subject: Re: [PATCH] mm: mempolicy: fix automatic numa balancing for shmem
Date: Thu, 23 Jul 2026 17:15:15 -0700 [thread overview]
Message-ID: <20260723171515.b5ddbc59c5c36ad01ef8f7fb@linux-foundation.org> (raw)
In-Reply-To: <amIrDncrL4K-JRBO@cmpxchg.org>
On Thu, 23 Jul 2026 10:54:06 -0400 Johannes Weiner <hannes@cmpxchg.org> wrote:
> > But in this case, IIUC, this change will "silently" enable NUMA balancing for
> > shmem-based KVM setups where it was previously disabled (albeit unintentionally).
> >
> > I'm not fundamentally opposed to the change, but I do worry that downstream KVM
> > users could be in for a nasty surprise.
It is a bit concerning.
> This should be very visible in early kernel validation after an
> upgrade. VM hosts tend to not do much else, with VM memory dominating
> the host. You'd expect a significant uptick in numa_pte_updates,
> numa_hint_faults, and a change in per-node nr_shmem stats. And the
> patch subject makes it trivial to find in a commit delta scan.
Is there anything we can do to make this process less painful?
Documentation of course, but what about detecting the situation and
emitting a once-off warning?
next prev parent reply other threads:[~2026-07-24 0:15 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-29 16:33 Johannes Weiner
2026-06-29 17:59 ` Gregory Price
2026-06-29 18:22 ` Johannes Weiner
2026-06-30 11:20 ` Huang, Ying
2026-06-30 15:29 ` Gregory Price
2026-07-01 11:03 ` Huang, Ying
2026-07-01 15:33 ` Gregory Price
2026-07-01 15:49 ` Johannes Weiner
2026-07-01 16:22 ` Gregory Price
2026-07-06 11:27 ` Huang, Ying
2026-07-06 17:30 ` Gregory Price
2026-06-29 18:33 ` David Hildenbrand (Arm)
2026-06-29 18:47 ` Johannes Weiner
2026-06-30 11:26 ` David Hildenbrand (Arm)
2026-06-30 23:40 ` Balbir Singh
2026-07-23 5:39 ` Yan Zhao
2026-07-23 13:51 ` Sean Christopherson
2026-07-23 14:54 ` Johannes Weiner
2026-07-23 15:58 ` Gregory Price
2026-07-23 17:07 ` Johannes Weiner
2026-07-23 17:48 ` Gregory Price
2026-07-23 18:45 ` Gregory Price
2026-07-23 22:30 ` Yosry Ahmed
2026-07-23 22:56 ` Gregory Price
2026-07-24 0:15 ` Andrew Morton [this message]
2026-07-24 3:55 ` Gregory Price
2026-07-27 16:37 ` Sean Christopherson
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