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[80.230.68.31]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47aa0f214d2sm33176455f8f.33.2026.07.07.07.01.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2026 07:01:59 -0700 (PDT) Date: Tue, 7 Jul 2026 10:01:55 -0400 From: "Michael S. Tsirkin" To: Lorenzo Stoakes Cc: "David Hildenbrand (Arm)" , Sourav Panda , muchun.song@linux.dev, osalvador@suse.de, akpm@linux-foundation.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, mhklinux@outlook.com, fvdl@google.com, gthelen@google.com, mike.kravetz@oracle.com, pasha.tatashin@soleen.com, rientjes@google.com, riel@surriel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [RFC PATCH 0/6] mm/hugetlb: Dynamic, NUMA-aware HugePage Cache & Free Page Reporting Message-ID: <20260707095843-mutt-send-email-mst@kernel.org> References: <20260707064235.1386552-1-souravpanda@google.com> <9624988a-366e-4884-9408-3f3b88c27290@kernel.org> <20260707062428-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: ra6UxLREpkxB7DLgS5RfavjMq9fMJE-wGtaT04sc-ak_1783432921 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: AB1E040010 X-Stat-Signature: 6trmhs7uoyshwpxg88ar6mokus6zgfpz X-Rspam-User: X-HE-Tag: 1783432923-589362 X-HE-Meta: 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 GSBq+ci5 k237gscQv0HYFhZAoXTcIfzI+0YCuWkQA9LC1JTmc573jjqCXGGNrGO9H8kgjq7nrqI8gQJVNyIo4XFvhkVGNNUSwD5yphdFRaE4vEEwZiV+XEwVtqeAOMM6r+gBvtsqnLyco2dBA3O4nwkSWQbuoc/ZxJCVcSh51KcuoBfqWIJpYR0TeSlukEqADaEFpwISKZ4cSQgo7sCXVtRXdNp+Mthu77fWgY3TxxMuzte17MzlK+npE+D6QkNwxYBeqzuG8mLB1DT2HIL6KVyHHz0dsyJOfu8jFT45MSTf3mrN5l4lY/LNVvY+4lsgGusJ/k26nUAsPVdln9LVw+lLtEX56NdweJg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jul 07, 2026 at 12:06:34PM +0100, Lorenzo Stoakes wrote: > On Tue, Jul 07, 2026 at 12:28:44PM +0200, David Hildenbrand (Arm) wrote: > > On 7/7/26 12:25, Michael S. Tsirkin wrote: > > > On Tue, Jul 07, 2026 at 09:29:07AM +0200, David Hildenbrand (Arm) wrote: > > >> On 7/7/26 08:42, Sourav Panda wrote: > > >>> Overview > > >>> This patch series introduces a dynamic, NUMA-aware HugePage Cache, > > >>> backed by a kernel shrinker to safely return memory under pressure, and > > >>> integrates it with Free Page Reporting (virtio-balloon) for HugeTLB, > > >>> specifically targeting gigantic (1GB) hugepages. The goal is to solve > > >>> the tradeoff between allocation latency and memory > > >>> fungibility in virtualized and heterogeneous cloud environments. > > >> > > >> Hi, > > >> > > >> in general, we consider hugetlb nowadays to be mostly in feature freeze, as we > > >> realized a while ago that adding more special casing on top of something too > > >> special for all of MM is only going to hurt us more in the long run. > > >> > > >> We want to have less special casing and less special sauce, not more. > > >> > > >> Now, there is nothing wrong in making hugetlb be less special, by making it use > > >> more of core infrastructure etc. > > >> > > >> But optimizing for surplus hugetlb pages by teaching hugetlb about new caches > > >> and its custom free-page-reporting support rather looks like the wrong direction > > >> for me? > > >> > > >> -- > > >> Cheers, > > >> > > >> David > > > > > > > > > It is currently bypassing free-page-reporting completely. > > > Making existing free lists not ignore free-page-reporting would > > > maybe considered "making it be less special"? > > > > > You have this completely backwards. > > You're advocating making hugetlb _more special_ by duplicating functionality that > core mm already supports. > > I mean: > > mm/hugetlb.c | 590 ++++++++++++++++++- > > Tells the whole story right? > > The whole issue with hugetlb is the very fact that it's a parallel > implementation of a bunch of mm stuff in its own little world. > > We make it less special by mm/hugetlb.c smaller and smaller and implementing > what it does sanely elsewhere in _core mm_. > > > > > Depends. We don't really want an orthogonal implementation of something we have > > in core-mm. > > Yes, exactly. > > Feature freeze means feature freeze, not 'feature that core mm doesn't support > feature freeze'. > > Hugetlb is a poster child for poor decision making in mm that has left us > saddled with maintenance nightmares because we allowed 'just one more feature > in' (TM) with little to no thought to the future. > > And we've all learned from that and don't want to repeat these kinds of > mistakes, nor make existing mistakes worse. > > And work to improve hugetlbfs and make changes like the above are VERY welcome > :) Fair enough. > Laying a foundation for hugetlbfs to be more of a sane mm citizen through rework > series is really the asking price for stuff like this in my opinion. Lorenzo, do you know *how* you want it reworked? Could you write it up at a high level? Because if not, it's not really practical to make it the asking price. > > > > -- > > Cheers, > > > > David > > Thanks, Lorenzo