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Thu, 01 Oct 2026 06:26:06 -0700 (PDT) Received: from gourry-fedora-PF4VCD3F ([2620:10d:c092:500::6:7dd1]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a01f93ad0bsm47435175e9.4.2026.10.01.06.26.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Oct 2026 06:26:05 -0700 (PDT) Date: Thu, 1 Oct 2026 09:26:03 -0400 From: Gregory Price To: "David Hildenbrand (Arm)" Cc: Zi Yan , Li Zhe , Joshua Hahn , akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, mhocko@suse.com, corbet@lwn.net, skhan@linuxfoundation.org, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/numa_balancing: allow migrate on protnone reference with MPOL_WEIGHTED_INTERLEAVE policy Message-ID: References: <20260930121154.687586-1-joshua.hahnjy@gmail.com> <2e3f12b7-0dac-428c-b70b-07e1f63de028@bytedance.com> <280965b2-c6eb-4f01-a0ac-c4fb7e518f97@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <280965b2-c6eb-4f01-a0ac-c4fb7e518f97@kernel.org> X-Stat-Signature: 4iyo6j5nqqi5td1b379kkou1fknj485x X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: E9EE040005 X-HE-Tag: 1790861167-659603 X-HE-Meta: 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 jdHVMOQz WxGnNASb71itxsH103jNUPMAdkKP2fefpyTtU2Q+OI0xjkGp4ywRfEIJ/Ie1s2r7b3NDjJtBXEUqhuxr0Zq4rfPgSnLY69/GRX+7TnKlD0mtvU90TjnmNhnZBIHKKr9B8SJA4ymXhW37iOzXJCTojpNCQ6+b1qm+WhRgI4e12BqlbLN0vZ43g+Va5rfhHCnYwOyJgWzhO0AnA8dVd4OlTZOMZ5Ac8QUq+VItn+nC/6R1/9mI64ZoFu80Wf972g+Zv+KfNbXqno+ION7muuVY7yMpOLy44MWgDoqaTrybJa2OyI9M2f39KHa61tJDh0mdmgVRyAOI73TxD0OyoGq5fP/M04EptRUkSBSSZ0isoerT6iS6w2ayYM+PtxtXCKufShiE00K5bv+lU0FZgNznzv/3owkjvmkkPnP92Sl9OcR799zckdR/kJ9UzHLjJwDTDZLD495yWo6pbPY+WuVu9d0JUUHi8WjMj/v17ExJhji2I5/k= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Oct 01, 2026 at 12:54:22PM +0200, David Hildenbrand (Arm) wrote: > > If this is a initial-fill problem, can userspace set weighted interleave > > initially? The program or harness can observe memory usage of the program > > or related NUMA nodes and switch the policy to numa balancing via > > set_mempolicy() or mbind() without MPOL_MF_MOVE after certain threshold > > is met? > > You mean: use the weighted policy initially and then switch to a NUMA-balancing > one which doesn't involve the weights anymore? > > That makes more sense to me. Although I struggle to see why an effectively > "let's put random memory on slow and others at hot" is a good starting point to > later let if be fixed up by actual balancing/tiering. > > It all sounds a bit hackish. :) > It is a bit of a non-combo (Nonbo). You're using weighted interleave with the intent of spreading out the bandwidth utilization (and maybe to offset some reclaim behavior? *shrug*) but then undo all the placement with tiering. But, in defense of the hackery - I have seen strategies like this work to optimize startup times and then let tiering optimize runtime. Phased execution gets funky like that. ~Gregory