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b=X5mnDEdTO9Je4v7S3JjNNPmfdm02Dpi0LuieTixZSV4wN86PdhIOr3YP08mWc3tke gKSVsPVhO8HO7tn9+hIKGqBVOAJJikTKoKNDZqf16CSCIIGYm9PRunFT+YZl5gt4+G 9tBUr5GTXeG+FTMYbyWYxBtuV4qo59oNuVm50OyNNNf9SGYg6tVwtJ/Uc3pwrU0OWM gotfjaTy6wChz5IKDTFA1kWatUy0HEU16usAuswSyn0gyVWjOda6f5c2+JH2pk2EzN UEVvXzZBOej+B4ZkzbzXcwOJgvgTfsIfPOJO1WZFITnQmSdCsBpaWg8K6K6mWUnC6O 93RnkBVsJ98tQ== Date: Tue, 2 Jun 2026 00:56:57 +0000 From: Yosry Ahmed To: Nhat Pham Cc: kasong@tencent.com, Liam.Howlett@oracle.com, akpm@linux-foundation.org, apopple@nvidia.com, axelrasmussen@google.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, bhe@redhat.com, byungchul@sk.com, cgroups@vger.kernel.org, chengming.zhou@linux.dev, chrisl@kernel.org, corbet@lwn.net, david@kernel.org, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jannh@google.com, joshua.hahnjy@gmail.com, lance.yang@linux.dev, lenb@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pm@vger.kernel.org, lorenzo.stoakes@oracle.com, matthew.brost@intel.com, mhocko@suse.com, muchun.song@linux.dev, npache@redhat.com, pavel@kernel.org, peterx@redhat.com, peterz@infradead.org, pfalcato@suse.de, rafael@kernel.org, rakie.kim@sk.com, roman.gushchin@linux.dev, rppt@kernel.org, ryan.roberts@arm.com, shakeel.butt@linux.dev, shikemeng@huaweicloud.com, surenb@google.com, tglx@kernel.org, vbabka@suse.cz, weixugc@google.com, ying.huang@linux.alibaba.com, yosry.ahmed@linux.dev, yuanchu@google.com, zhengqi.arch@bytedance.com, ziy@nvidia.com, kernel-team@meta.com, riel@surriel.com, haowenchao22@gmail.com Subject: Re: [PATCH v6 01/22] mm/swap: decouple swap cache from physical swap infrastructure Message-ID: References: <20260505153854.1612033-1-nphamcs@gmail.com> <20260505153854.1612033-2-nphamcs@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: 97B9F40007 X-Stat-Signature: 5puo7zmri4x7tgz1478oadfi9e4bown5 X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1780361821-890564 X-HE-Meta: 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 +bWX4I78 6xeMyznnhzZvFMxLkKNp/R+rxxBGWzFPtikTH8EC0kyTAlEqxkJ7qhnMjs8CaV6xXA2u66LzZ//c85WObxIdCg1djJHiwX+rJArHq9jYpr4Vi9KkEyQCoTx4OllZFmIYCnqNsfrt8xKdzqk5mhmZu6jMLrzNOtBoSxllteDsRPv8CqpejqVhAqT/9hREuKRA9BrPrNp/Vu2K6QqBFT2CdcRwsiHt24w6kn3KmiUgmkCSbQY8CN6B+f++ULy3yEgOBJj9CH7ZShFYdoM+DLuxK2Uaoss+hQpULDaZPjPlcCl7Lca4uLyNg6FWpcKHUbI7dKv6ueNsn9xBJgWmv2O3TfTIKe2Jgyi/woD+M3DBEmfMvNsnk0aaKo4PA9SLyH6HqBbS/n/wU+1wLUVY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, May 28, 2026 at 02:42:19PM -0700, Nhat Pham wrote: > On Mon, May 11, 2026 at 3:46 PM Yosry Ahmed wrote: > > > > On Tue, May 05, 2026 at 08:38:30AM -0700, Nhat Pham wrote: > > > When we virtualize the swap space, we will manage swap cache at the > > > virtual swap layer. To prepare for this, decouple swap cache from > > > physical swap infrastructure. > > > > > > We will also remove all the swap cache related helpers of swap table. We > > > will keep the rest of the swap table infrastructure, which will be > > > repurposed to serve as the rmap (physical -> virtual swap mapping) > > > later. > > > > I didn't look through the entire series, but let me ask the same > > high-level question I asked before. Instead of moving things out of the > > swap table, why not reuse the swap table as the representation of the > > virtual swap space? Seems like most/all metadata is already moved there > > in a nice concise format. > > The honest answer is I wasn't sure it would work, so I was hacking > quietly a prototype on my own time :) > > I finally got something that survives stress-ng and constant > memory.reclaim thrown at it though. I figured I should send it out to > get feedback before digging myself deeper into that hole: > > https://lore.kernel.org/all/20260528212955.1912856-1-nphamcs@gmail.com/ > > There is still a small problem left (the metadata duplication issue > that Johannes brought up). It is potentially fixable, but I haven't > actually tried it out yet, so I don't want to overstate here. But take > a look at it and let me know how you feel about this alternative > approach! Thank you! I will take a look!