From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D920219DF99; Thu, 31 Oct 2024 14:35:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730385307; cv=none; b=YeFMOElMj5F7DFSqHuZpSF7y4vBVRl64VfqogF3oy4SJGB3Bgqlo5gnCqgkAasfW/mSeeu82Nsc+rtkMM+ml+jh+J3gUmwg5VoFDgVHmo5O+5tm2B3iAErhqeftF1CYSgLMswcbuuBRbNDT5f1Aos+ULftLG8KknzxbPWDYNiCU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730385307; c=relaxed/simple; bh=908GH7IBG1XfA0L7MNM6eq8gsxx7GOrv1X37ET8DUyw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=UZ0VvXxEUGkrJyO4bOPGNnUZUQA/9/2U0NOJaX8Y0Lc1D9KWE/vVv144CMm/uZgREIVaxrfq0fGitNMXxYq2B5GkKxxhfjgILW1DJuGAd6wVHYAXCBmgET98XFGehKiwljRR0e0QuA1DSSGq6l9pCkPMPKlgUayNp9KWnLiAgd4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AzERKkIR; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AzERKkIR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 84EEAC4AF1B; Thu, 31 Oct 2024 14:34:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730385306; bh=908GH7IBG1XfA0L7MNM6eq8gsxx7GOrv1X37ET8DUyw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=AzERKkIRwC/O4kQ8lXH0L4xaw8lcCpG9teRlnbXLQORdNS/jid5oXobAIqrFBvnMj 8TavotafNAjfch6gf0LzZd7t4y0STCY6OrBp4+pmufLdZw1Fob2IJ4RKCx1QlAfwV9 igjdjueqvbXLikgcF2avFhhxK4GjtzcQFneRgzqKo5j+kDvdftzhJhDxhFK67/RAo3 ZZnTPKmuxzBoEiw+4Nr6Ej07BMw2Avy0n+cNU0B+udrtpRzcAdUbRXmmbF8dH36io5 ZNTxQC63JDz1vnx9yl/KoBYUc48LeRNVURbhd+I75R8XMmmDJU2+T05l6ZtsAZv4qg xvwr8D+8DX0Bg== Date: Thu, 31 Oct 2024 16:31:03 +0200 From: Mike Rapoport To: Gregory Price Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org, linux-cxl@vger.kernel.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, david@redhat.com, osalvador@suse.de, gregkh@linuxfoundation.org, akpm@linux-foundation.org Subject: Re: [PATCH v4 1/3] memory: implement memory_block_advise/probe_max_size Message-ID: References: <20241029202041.25334-1-gourry@gourry.net> <20241029202041.25334-2-gourry@gourry.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241029202041.25334-2-gourry@gourry.net> On Tue, Oct 29, 2024 at 04:20:39PM -0400, 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 | 48 ++++++++++++++++++++++++++++++++++++++++++ > include/linux/memory.h | 10 +++++++++ > 2 files changed, 58 insertions(+) > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > index 67858eeb92ed..099a972c52dc 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -110,6 +110,54 @@ static void memory_block_release(struct device *dev) > kfree(mem); > } > > +/** > + * memory_block_advise_max_size() - advise memory hotplug on the max suggested > + * block size, usually for alignment. > + * @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 identify the largest supported alignment for all sources. > + * > + * Use of this value is arch-defined, as is min/max block size. > + * > + * Return: 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_advised_size_queried; kernel-doc will be unhappy about variable declarations between the doc block and the function it describes > +int memory_block_advise_max_size(size_t size) > +{ > + if (!size || !is_power_of_2(size)) > + return -EINVAL; > + > + if (memory_block_advised_size_queried) > + return -EBUSY; > + > + if (memory_block_advised_sz) > + memory_block_advised_sz = min(size, memory_block_advised_sz); > + else > + memory_block_advised_sz = size; > + > + return 0; > +} > + > +/** > + * memory_block_advised_max_size() - query advised max hotplug block size. > + * > + * After the first call, the value can never change. Callers looking for the > + * actual block size should use memory_block_size_bytes. This interface is > + * intended for use by arch-init when initializing the hotplug block size. > + * > + * Return: advised size in bytes, or 0 if never set. > + */ > +size_t memory_block_advised_max_size(void) > +{ > + memory_block_advised_size_queried = true; > + return memory_block_advised_sz; > +} > + > unsigned long __weak memory_block_size_bytes(void) > { > return MIN_MEMORY_BLOCK_SIZE; > diff --git a/include/linux/memory.h b/include/linux/memory.h > index c0afee5d126e..07e20a77b717 100644 > --- a/include/linux/memory.h > +++ b/include/linux/memory.h > @@ -149,6 +149,14 @@ static inline int hotplug_memory_notifier(notifier_fn_t fn, int pri) > { > return 0; > } > +static inline int memory_block_advise_max_size(size_t size) > +{ > + return -ENODEV; > +} > +static inline size_t memory_block_advised_max_size(void) > +{ > + return 0; > +} > #else /* CONFIG_MEMORY_HOTPLUG */ > extern int register_memory_notifier(struct notifier_block *nb); > extern void unregister_memory_notifier(struct notifier_block *nb); > @@ -181,6 +189,8 @@ int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func, > void memory_block_add_nid(struct memory_block *mem, int nid, > enum meminit_context context); > #endif /* CONFIG_NUMA */ > +int memory_block_advise_max_size(size_t size); > +size_t memory_block_advised_max_size(void); > #endif /* CONFIG_MEMORY_HOTPLUG */ > > /* > -- > 2.43.0 > -- Sincerely yours, Mike.