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[50.32.2.77]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-56a6546198fsm878831173.21.2025.09.25.08.09.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Sep 2025 08:09:01 -0700 (PDT) Date: Thu, 25 Sep 2025 11:08:59 -0400 From: Gregory Price To: Jonathan Cameron Cc: Yiannis Nikolakopoulos , Wei Xu , David Rientjes , Matthew Wilcox , Bharata B Rao , linux-kernel@vger.kernel.org, linux-mm@kvack.org, dave.hansen@intel.com, hannes@cmpxchg.org, mgorman@techsingularity.net, mingo@redhat.com, peterz@infradead.org, raghavendra.kt@amd.com, riel@surriel.com, sj@kernel.org, ying.huang@linux.alibaba.com, ziy@nvidia.com, dave@stgolabs.net, nifan.cxl@gmail.com, xuezhengchu@huawei.com, akpm@linux-foundation.org, david@redhat.com, byungchul@sk.com, kinseyho@google.com, joshua.hahnjy@gmail.com, yuanchu@google.com, balbirs@nvidia.com, alok.rathore@samsung.com, yiannis@zptcorp.com, Adam Manzanares Subject: Re: [RFC PATCH v2 0/8] mm: Hot page tracking and promotion infrastructure Message-ID: References: <20250910144653.212066-1-bharata@amd.com> <7e3e7327-9402-bb04-982e-0fb9419d1146@google.com> <20250917174941.000061d3@huawei.com> <5A7E0646-0324-4463-8D93-A1105C715EB3@gmail.com> <20250925160058.00002645@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250925160058.00002645@huawei.com> X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 6BE11C0016 X-Stat-Signature: eha3go6fgzpx6rech9xfn457sptoiixh X-Rspam-User: X-HE-Tag: 1758812943-616709 X-HE-Meta: U2FsdGVkX1/e16ffOsLwVdG1Rg9x1bvP85H0xZmTHrZtxlRlHbfIjDkxcbLan+Zks1E3alVsiQTU/yu1RBoMp1c/RA1OJ9NVy6Y4UD8Ss5ERofJT+TLOj9yaiTKdfMPmPUr5SJ5veWZYoskBoDXKdMvgsZummBoNo1nTSVgqaQNzMG1tlEh7VONKNkXxCdyVmxrHO+wJL2WCF9u3gtzopygUsdX4K6aLuSe7AUWO60PsG5edmIlLVYwc/GJqU5HkCqyE2eGudV1syvXDNGX8dOnELsav5yh0E+fmW/9HhXvlmI4qcBE19kczat0N0egzMRAFCdDtS/YEtcdfA37dxhiWGnm1UTa8UCiXsxN3eMJNINddkIlPA3WtQEsplGRT29k6mqvau17z9rLq+xkpojHodM+o7SCdiHl9O6gQDJtMKh0ajDeJBC8waCw2hGDSgarKQP8pg+//wlDrwgrZvM6ptrJnzlXP3P7ogvWfc3N72eHDipEGWAh7VHkloxtESDmETSKXq7efWg/KAnsHhpQFzFZX7mcNB4XeNGtJZLnkF6QeaVg7T6BIIA+t+TdF1Esq5T6okNIprMPc25JYZ7xeZs+XmhM0awNhb9XXmM4a1sExaGjMNZBIwejQ/ZUkRB3YwH6rSSvN+OeKp4Ym3PEQ8apb0sIysF/VFoKD3RSAOOxd2+1dGX+WFWVdrN5w4c036xyog/x1GdJHyi3PWsxi2aXcJeBFRUWg4gTtk0zE/Ly/v33wlrKcw6f25A48D58SZWH3hNv1+vMt2xWu8Ea8/JLpPCEyHHiJLi1cEzrxfRYvnOaP2rJfncUJbtqooOa79HgZuWyVmVwczlR4gGy7OqBY8G9EPd3FburbICFgAMnDdaATWjne3h+1b0H4g90gdN06T98qVdrtK5Xyryiy0SsIxae+ztlCfMo3Sd33TOzk05bDhGAghjD1dIIzmiBkxdlP9nMbxUdQmhD WBtubDh4 HKPMsFCmEFOEETpcbwcSeV04WElhl758Gz+tmVke7A9ANN1z1nJOl6WYVwnewSTodcKP5CCeGjezpb2h/QHsRIvOt1Vsm+CzskqRrB+qFEQgvP0Tvcv2LrQjU5l0L+2V05yZjKpQ7CujIa1IYwrKqarkNNvu6ajTWSm0Huhklrl16mz0XfoiReAKo/hgiAkyD/QiMeGb/rVRfOc2JLvgtV1mXPb7zG7YVUgP0aJW0DqG47DRQbivAavs391oGA7DGY8J2vIqz7mNc+1sE5G9GO5hrkjVt2yTtD5wtKt7+i5PNZ4rBXUW6cXtAhfXakHmH0zcEnNbaySMQk05BXoXoHFUYohqrlS6Eokuah4Wrl079Gsryhhfj0Ti4mJbb3bCaWXZZl9L9BsANH6BgXzmNusEcDzOED/GPA/diInbECtakREs= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Sep 25, 2025 at 04:00:58PM +0100, Jonathan Cameron wrote: > Now, if we can put this into a special pool where it is acceptable to drop the writes > and return poison (so the application crashes) then that may be fine. > > Or block writes. Running compressed memory as read only CoW is one way to > avoid this problem. > This is an interesting thought. If you drop a write and return poison, can you instead handle the poison message as a fault and promote on fault? Then you might just be able to turn this whole thing into a zswap backend that promotes on write. Then you don't particular care about stronger isolation controls (except maybe keeping kernel memory out of those regions). ~Gregory