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[2003:cb:c72d:8500:d87a:ed8e:1e80:5a7e]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4318b56facasm172541035e9.33.2024.10.29.05.39.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 29 Oct 2024 05:39:45 -0700 (PDT) Message-ID: <2e90cce3-7a75-4827-81f1-01d9641c1b75@redhat.com> Date: Tue, 29 Oct 2024 13:39:43 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/3] memory: implement memory_block_advise/probe_max_size To: Gregory Price , x86@kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org Cc: linux-cxl@kvack.org, Jonathan.Cameron@huawei.com, dan.j.williams@intel.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, osalvador@suse.de, gregkh@linuxfoundation.org, akpm@linux-foundation.org, rppt@kernel.org References: <20241022213450.15041-1-gourry@gourry.net> <20241022213450.15041-2-gourry@gourry.net> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 48111140018 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: u5br5jrpmniw5ajxqtu5hrpohktg8e6w X-HE-Tag: 1730205575-155442 X-HE-Meta: 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 athW4BZH 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 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 22.10.24 23:34, 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. > > Suggested-by: Ira Weiny > Signed-off-by: Gregory Price > --- > drivers/base/memory.c | 43 ++++++++++++++++++++++++++++++++++++++++++ > include/linux/memory.h | 10 ++++++++++ > 2 files changed, 53 insertions(+) > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > index 67858eeb92ed..a0fd9e1451aa 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -110,6 +110,49 @@ static void memory_block_release(struct device *dev) > kfree(mem); > } > > +/* As Mike says, this documentation looks incomplete. /** * memory_block_advise_max_size: suggest a maximum memory block size ... > + * @size: suggestion for maximum block size. must be aligned on power of 2. > + * > + * Early boot software (pre-allocator init) may advise archs on the max block > + * size.This value can only decrease after initialization, as the intent is to Missing space after "size." > + * identify the largest supported alignment for all sources. > + * > + * Use of this value is arch dependent, as is min/max block size. > + * > + * Returns: 0 on success > + * -EINVAL if size is 0 or not pow2 aligned > + * -EBUSY if value has already been probed > + */ > +static size_t memory_block_advised_sz; > +static bool memory_block_size_probed; > +int memory_block_advise_max_size(size_t bz) > +{ > + if (!bz || (bz & (bz - 1)) != 0) > + return -EINVAL; > + > + if (memory_block_size_probed) > + return -EBUSY; > + > + if (memory_block_advised_sz) > + memory_block_advised_sz = min(bz, memory_block_advised_sz); > + else > + memory_block_advised_sz = bz; > + > + return 0; > +} > + > +/* > + * memory_block_probe_max_size provides a suggested maximum memory block > + * size value. After the first call, the value can never change. > + * > + * Returns: advised size in bytes, or 0 if never set. > + */ > +size_t memory_block_probe_max_size(void) Can we call that "memory_block_advised_max_size()" ? > +{ > + memory_block_size_probed = true; Call this "memory_block_advised_size_queried" ? > + return memory_block_advised_sz; > +} -- Cheers, David / dhildenb