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t=1787857496; bh=l0/18a+jAXPQl28qEPQ6uj9wzdNRM90aKlsTE3XVMSs=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=IlYnxvrh2yDgFzTmXYpXAblj4oY6DF62sHqpe9c1DGkpNWRoTeFoataC7x+TPDk+D 5ZpoJDkYw5xUrFJSK9rIzvGFROXkjqIK/sj1//S8MEoMhpvZ7egEv+DR0tAWav6VAh Tk+z/ORfHyrXgtbx8UFQeGO3ds9ogqUc8uPJQdJbp4XBJaSTIQ7p0zNQAMZrBtLR9I Ma7+fmGyJlg9zJigXjp+fagb/cUpv8EuVCgbkmt4n2wplDJVsZ5mtSuY9VOGlyPBCZ R9hijTRWxt0jrSJFewQ28XCNVr7u/CA1FwfhVLiDHcQJjxmpPqzycazMIaFgODYIha v71IFBB7rBzqg== Message-ID: Date: Thu, 27 Aug 2026 21:04:48 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 00/18] mm: arm64: Add kernel replication feature To: "Lorenzo Stoakes (ARM)" , artem.kuzin@huawei.com Cc: catalin.marinas@arm.com, akpm@linux-foundation.org, vbabka@kernel.org, cl@gentwo.org, linux@armlinux.org.uk, will@kernel.org, mark.rutland@arm.com, liam@infradead.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, wangkefeng.wang@huawei.com, panov.nikita@huawei.com References: <20260827161158.3618409-1-panov.nikita@huawei.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: AD805180009 X-Stat-Signature: fzpnpe8pc6gm131znhf336ac74xpe9wn X-HE-Tag: 1787857497-466364 X-HE-Meta: U2FsdGVkX18omJW328yVe4fGXum+FDzpsb9/fdAgnGzhQw/e3bhRwAcWANT1BkllRHAl7ONjeP/WgyjFO2BDrWCxp6dpv64q0HjUogHJ+A1o6RqmOvYTvQnDScDT7CyDAu98fF3UZBuCjClRC+qd8FeNsbnEOvujKFaXRNsUx/euiMIl2+tfis7aRg69hjT20r1xSlfLKi0iZuWHDVx+GFD91P3f4r+QB7FiRWcK+LOYMDhC60CcyohfcfLbpCLoa26kGhmvw5F7dBRlOtc7sR0PRQKlzIQbJ1/FRycIFmzYbdwu9enjs/ndi80/mRwsuPvVJQduzBmiUUEINd2Ui1daCtHzMzv7LPhytUq9Wb2pafse6sxvI7k4V/l78ei4U1dSrQlqasxHv6a0WtYMcN0bHxzuej/A9iKYcGFNv6TR5l68LH+054gBMF+WHg6eEUsPrcstiAf+MFEUuwUyT1FvtWHLR2KaMGNNIxNeC59OSArN2sdtEd/ezJyUPVbXjoRESlOBvg+kY+itsFy3Lf3+l2+WSkSUgqtUC6/fLFiSzJqaxB4L7THLLA9kw+V4obvBurXam6P7yF81SgfGjgQhJhBi/z/Uid4FRjJXNaz7mKmoTSSafU8yN4dMa2DsnIAtS9vG6kDrWCge3zwkeGSvMnA+6U9A+4J61h2XILKV9rlfMkcbdiMTz5OgL6PXBwYeqLDuWei+WM0wVIJb4Jd/kWlyA5ynUxCn4GgSG7oWI5h5g5DPsYZeXb57VKJ7JwUM6T6rFRayTZCpikLTHQwn/a/xf0nLYdZgnDMpystftsSXEKIUKIhhuZMkiKT0F8TMa5Fz8wSuupej5Cpd1/CF2BQ45iqHFvm2WpB9kQxgGnGOEje3CpmOGhiw9jDZYaaBNwNc7L1q1PR79Yh4H5A59ankUvKVgwfZhZ1gBBEIKzNHMdPMF+OGvG7FqXIzcJkVbDgR8fc38bIEiyJ TeYxNnZD DfI5+Q2w2Dn+GeAVqk4J/raZtbeY71VsOlEMjwrJ0+KQNutmGtGBwWA/34DXJhLVzfC4bKMVvQNSDl9rMBYUc3FzAwH/vAHJJfm1LB7ymMkwcZNYDLFRVGhkSrUPeXDZtGDdefv1VX3Ky7IVm+G/2b70AY7WdNj4kLg8GRChf5nWKYpVjHRqM6l9/YeCh7HQpOjPk+mK0egC2ej/NLcoL1btVV1Pb1QXeBtm4vK1rTz4uBgx4/kB7gyv3nZvnpsno+1uT Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: [...] About to go on PTO, some random points :) > >> [12] - Optimize this_cpu_*() ops for non-x86 (ARM64 for this series) >> >> As of today, none of it was merged into mainline. > > I mean :) maybe take that as a hint? If a number of series trying to do X get > rejected by upstream, that is maybe suggestive of barking up the wrong tree? I'd have expected an explanation at that point why previous approaches were not merged and how this patch set is sufficiently different that it is worth maintainer's time. > >> However, after thorough re-evaluation, we were not able to observe >> performance improvement for the x86 platform, so we have decided to stop this >> direction and switch on arm64. > > I mean, why? You should provide details here, this is quite hand-wavey. You are > also proposing core mm changes for something that seems specific to unique > hardware as far as I can tell, which is a big ask. What I consider interesting is "after thorough re-evaluation, we were not able to observe performance improvement for the x86 platform". How confident are we that a thorough re-evaluation on arm64 will not similarly have the same outcome? IOW, what was the problematic part when doing the x86 evaluation, and how was that avoided when evaluating the arm64 implementation? -- Cheers, David