linux-kernel - Re: [PATCH v2 1/2] driver/base: Optimize memory block registration to reduce boot time

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Message-ID: <aBHTeeAWtlrt4gN8@localhost.localdomain>
Date: Wed, 30 Apr 2025 09:38:33 +0200
From: Oscar Salvador <osalvador@...e.de>
To: Donet Tom <donettom@...ux.ibm.com>
Cc: Mike Rapoport <rppt@...nel.org>, David Hildenbrand <david@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>, rafael@...nel.org,
	Danilo Krummrich <dakr@...nel.org>,
	Ritesh Harjani <ritesh.list@...il.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Alison Schofield <alison.schofield@...el.com>,
	Yury Norov <yury.norov@...il.com>,
	Dave Jiang <dave.jiang@...el.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] driver/base: Optimize memory block registration
 to reduce boot time

On Mon, Apr 28, 2025 at 10:33:46PM +0530, Donet Tom wrote:
> During node device initialization, `memory blocks` are registered under
> each NUMA node. The `memory blocks` to be registered are identified using
> the node’s start and end PFNs, which are obtained from the node's pg_data
> 

Hi Donet,

> Test Results on My system with 32TB RAM
> =======================================
> 1. Boot time with CONFIG_DEFERRED_STRUCT_PAGE_INIT enabled.
> 
> Without this patch
> ------------------
> Startup finished in 1min 16.528s (kernel)
> 
> With this patch
> ---------------
> Startup finished in 17.236s (kernel) - 78% Improvement

That is pretty impressive.

> +void register_memory_blocks_under_node_early(int nid)
> +{
> +	struct memblock_region *r;
> +	unsigned long start_block_id;
> +	unsigned long end_block_id;
> +	struct memory_block *mem;
> +	unsigned long block_id;
> +
> +	for_each_mem_region(r) {
> +		if (r->nid == nid) {
> +			start_block_id = phys_to_block_id(r->base);
> +			end_block_id = phys_to_block_id(r->base + r->size - 1);
> +
> +			for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
> +				mem = find_memory_block_by_id(block_id);
> +				if (!mem)
> +					continue;

I would just mention what David already said here, reduce identation,
and maybe declare the variables where they are needed. It might be clearer.

> +
> +				do_register_memory_block_under_node(nid, mem, MEMINIT_EARLY);
> +				put_device(&mem->dev);

I will comment on the "context" on patch#2.

> +void register_memory_blocks_under_node_early(int nid);
static void ... ?


-- 
Oscar Salvador
SUSE Labs