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 6A9441DE4D1; Mon, 28 Oct 2024 17:31:19 +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=1730136679; cv=none; b=spKtT/S0OqX8EJGnpOVdc1lUHWgi7G1YQ4WaB50YJSBGAnH8p3YfRop9Qy19UD1P8iFX16J5PRocVGbGqp0IWgv5Su+zFXG5a8CiZcQBETcAJ4NY3RAQesb27WqxqX/5SoLMSiZjOb0LaM3HP1ns8ixWU8rBW3kHskoaOvaLNX8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730136679; c=relaxed/simple; bh=RW3lMh/hj64PO7Sxfncf66yFZBftog/9Sb9K431heYE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HuqAv06Ue86D784ElbVuZ0Ync3SRk+/OIb9CmO+H5VBCx+8eDlNvcWfoifqvYO+X3Rne9tdocXJFSp9aUmk715vlVUfHM8X7JtxOA6mAmkyg20b4j6OKPYKKP+j2iKCo9gfCFoq9wgFIv3PaM7D9oIaNMCnaWT+Uero90Zv2yrs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DilTPWI2; 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="DilTPWI2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4873EC4CEC3; Mon, 28 Oct 2024 17:31:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730136679; bh=RW3lMh/hj64PO7Sxfncf66yFZBftog/9Sb9K431heYE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=DilTPWI2rFgKWdJkDIDILeTnqKWiYmCXqWlmb54U6CJf8qTHZG7M+r6aRuSON/xE/ j2SBn7YoNdGJlf6/tm5g4S+P46+f3B7MDcjGb2dYnqkOwgsX7cmojrKu+dhc7jZObe /ssvsoriqq/SeLAZCqUIMMrZjbPGDlPJhf3Ll6eSJQRHzh2A/gkb8t6WIqiw/HYh3K r8mymXC0YzRE8HzAAeU9r6SJrJtiYmdcuKTlzPCabdY5yoye0XK3SGLZUzZOV8M/gR 3MtR2Vlgj9jVkkfzVJE/zAx3eosYhNyyuM+A8js5cNEtUdYEQqKXGaqAp5zve5MES0 QvS50wM/odG7A== Date: Mon, 28 Oct 2024 19:27:21 +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@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, david@redhat.com, osalvador@suse.de, gregkh@linuxfoundation.org, akpm@linux-foundation.org Subject: Re: [PATCH v3 1/3] memory: implement memory_block_advise/probe_max_size Message-ID: References: <20241022213450.15041-1-gourry@gourry.net> <20241022213450.15041-2-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: <20241022213450.15041-2-gourry@gourry.net> Hi, On Tue, Oct 22, 2024 at 05:34:48PM -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 | 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); > } > > +/* If the intention for this to be a kernel-doc comment it should start with /**, should be placed right before the documented function and start with a brief function description > + * @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 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) size seems to me a better parameter name :) > +{ > + if (!bz || (bz & (bz - 1)) != 0) we have is_power_of_2() > + 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; > +} > + > +/* should it be kernel-doc? > + * 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) > +{ > + memory_block_size_probed = 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..47c00d6e1165 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_probe_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_probe_max_size(void); > #endif /* CONFIG_MEMORY_HOTPLUG */ > > /* > -- > 2.43.0 > -- Sincerely yours, Mike.