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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7b32ac44082sm652302085a.38.2024.11.12.20.15.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Nov 2024 20:15:20 -0800 (PST) Date: Tue, 12 Nov 2024 23:14:55 -0500 From: Gregory Price To: Dan Williams Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org, linux-cxl@vger.kernel.org, kernel-team@meta.com, Jonathan.Cameron@huawei.com, rrichter@amd.com, Terry.Bowman@amd.com, dave.jiang@intel.com, ira.weiny@intel.com, alison.schofield@intel.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, rafael@kernel.org, lenb@kernel.org, david@redhat.com, osalvador@suse.de, gregkh@linuxfoundation.org, akpm@linux-foundation.org, rppt@kernel.org Subject: Re: [PATCH v6 1/3] memory: implement memory_block_advise/probe_max_size Message-ID: References: <20241106155847.7985-1-gourry@gourry.net> <20241106155847.7985-2-gourry@gourry.net> <6733c86390c40_10bc62945f@dwillia2-xfh.jf.intel.com.notmuch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6733c86390c40_10bc62945f@dwillia2-xfh.jf.intel.com.notmuch> X-Stat-Signature: rpqm6it15tf5ksti3dhnn4swgrwj6bie X-Rspam-User: X-Rspamd-Queue-Id: 622F2120002 X-Rspamd-Server: rspam02 X-HE-Tag: 1731471264-153925 X-HE-Meta: U2FsdGVkX19YEQ5I0fkzqj3llEtp88fblc4G5SUOLmLObzcOiARG8296DIJ+drygE/W0EigwL2IrXYNX+KZR341QL+qpKJ6Z69RCNmMIOO+TAtXzfFZ+FMCddavTqIMRPgXzIGCJaWrB6vFmdTv7NggW5AQ82Qac5j0SPh6E1QXqt7TWcVTkSsXPoGIEuNSz4ODo2u7eVCNQBhHLcH0fa0vPheRmZfTzaDqgqCG5TOEFz/HEJDPNzpIJNF+UF0RLPjkpaJvUs2Yl2yXHr1iFYJwgrMmgHGOmld/o3iYXgYXIKJfrf5MYGn4gQcSwVHkNcXHXZoNXUnyQqhrQinT4enloW+sIkKOojcqdnPHO0ICOUOrx1hzg//2mAH9nr1jM+lC/bsb5AuWpacqr8nEWr9ThBHK6E7/RH1B/mHbN2pm8ekMQIeoWbThHMlwAT2WR2bR4vhFQTNMewELkEx6bm0GNy4ONjnxQ8Q2V9KAL0cftQtfyRkTyZi/tBl/0n/ZTnpdN8m2mUCE+DsKcLHC94HCFmcIK9Ex11SmI4DrfTxJXBM14amoWkPyltNtlSmdGX7VHsGIg/nNwN3y8sAW/ECFdfQYfd3DTfoid5K9RMYLPz/fk8gdkmC2XCARbci2EVnhH7otM2b6NdhwJJK/qjiiV2ISvaTaSMYYH7S6OzX1A/nWwDwigloSoefG70Y5GLvXwFRouezehmKY7E+DiCCtK6wPu1GIJRlHHAuR35tYFK88pQ2Bfqnd3A7KPhgDPr/ocrAJ6Nah7MAtGkhWE0W6EfSARNCV66K905mGS6/2EnPkUkNskF3wIF+f1mTjPRy0u0NvVButsbI1U1FYc4DUdXIEuABXGLz7rBuJQSvHNkQnM1rkaaK7exQq6MoLEj7PLbADcKk2fcqovhFBW3RsKtdojXz9emUnZOQSWd6caNS7uogzZF2m/oCOuxMNXj3ITHmOfEfDumux1FzB 7sKTvoXd RY68SJo1/Gdz3WVtAHvXOR3l8REzsmLFKYFlGKmVO6BIr00xfMXnSFa6wVe3sXmdVNZ6/K117FhgBoK+/KdgV9py3ZKSIWBwwDVRbP4osHL3ZQ7MsxQH/Ed4f13ax5hX9+H1Q++Kx3SiBCQtgjVJQV4DDAsn5YMnT2gDY7lVe8LZ1/dqt03S4JRCCwpnwIAyLDRHEaT9eqdqX4tuphhm2epC/gZo5+RQCkumlfUBQiliapGgAxkzgfqCIlNfozNZ/eLWI2Dz0QvrV5QA5dAmDWguRJGtSTbQK596niJhjpr4dKqtZBNF/vsM1REy1TEPMumj58VC7jtAl3CMZu2ps93KhlNzcpXLHmLDAHsqh9+6WS6A= 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 Tue, Nov 12, 2024 at 01:28:03PM -0800, Dan Williams wrote: > Gregory Price wrote: > > Hotplug memory sources may have opinions on what the memblock size > > should be - usually for alignment purposes. For example, CXL memory > > extents can be 256MB with a matching alignment. If this size/alignment > > is smaller than the block size, it can result in stranded capacity. > > > > Implement memory_block_advise_max_size for use prior to allocator init, > > for software to advise the system on the max block size. > > > > Implement memory_block_probe_max_size for use by arch init code to > > calculate the best block size. Use of advice is architecture defined. > > > > The probe value can never change after first probe. Calls to advise > > after probe will return -EBUSY to aid debugging. > > > > On systems without hotplug, always return -ENODEV and 0 respectively. > > Should the advice just succeed when the result does not matter? > I figure at some point during __init the value will be probed and subsequent calls will be ignored. I'd rather fail explicitly in that case to assist debugging - otherwise it might be a little maddening to discover your callsite is too late in the process. > Otherwise, it depends on the caller to not care based on config. > > I do not feel that strongly about it, so either way: > > Acked-by: Dan Williams