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From: Shakeel Butt <shakeel.butt@linux.dev>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: lsf-pc@lists.linux-foundation.org, 
	Johannes Weiner <hannes@cmpxchg.org>, David Hildenbrand <david@kernel.org>, 
	Michal Hocko <mhocko@kernel.org>, Qi Zheng <zhengqi.arch@bytedance.com>, 
	Lorenzo Stoakes <ljs@kernel.org>, Chen Ridong <chenridong@huaweicloud.com>, 
	Emil Tsalapatis <emil@etsalapatis.com>, Alexei Starovoitov <ast@kernel.org>, 
	Axel Rasmussen <axelrasmussen@google.com>, Yuanchu Xie <yuanchu@google.com>, Wei Xu <weixugc@google.com>, 
	Kairui Song <ryncsn@gmail.com>, Matthew Wilcox <willy@infradead.org>, 
	Nhat Pham <nphamcs@gmail.com>, Gregory Price <gourry@gourry.net>, 
	Barry Song <21cnbao@gmail.com>, David Stevens <stevensd@google.com>, 
	Vernon Yang <vernon2gm@gmail.com>, David Rientjes <rientjes@google.com>, 
	Kalesh Singh <kaleshsingh@google.com>, wangzicheng <wangzicheng@honor.com>, 
	"T . J . Mercier" <tjmercier@google.com>, Baolin Wang <baolin.wang@linux.alibaba.com>, 
	Suren Baghdasaryan <surenb@google.com>, Meta kernel team <kernel-team@meta.com>, bpf@vger.kernel.org, 
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [LSF/MM/BPF TOPIC] Towards Unified and Extensible Memory Reclaim
 (reclaim_ext)
Message-ID: <acUxJpJDzA7Bibob@linux.dev>
References: <20260325210637.3704220-1-shakeel.butt@linux.dev>
 <20260325190547.abb7309fb63473b57b7a90a0@linux-foundation.org>
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On Wed, Mar 25, 2026 at 07:05:47PM -0700, Andrew Morton wrote:
> On Wed, 25 Mar 2026 14:06:37 -0700 Shakeel Butt <shakeel.butt@linux.dev> wrote:
> 
> > We should unify both algorithms into a single code path. 
> 
> I'm here to ask the questions which others fear will sound dumb.
> 
> Is it indeed the plan to maintain both implementations?  

I think in general the plan/wish was to have one implementation but the current
state shows that we are far from where we wish to be.

> I thought the
> long-term ambition was to knock MGLRU into shape and to drop the legacy LRU?

That might be the ambition but I don't think there was an agreement and there
weren't any efforts to do so. Traditional LRU has been battle tested for decades
and thus there were concerns/skepticisms about this ambition as well.

To me, the right way is to take step-by-step approach with clear evaluations and
comparison on unifying or selecting a component from one over the other.